 M. F. J. Fox , B. M. Zwickl, and H. J. Lewandowski, "Preparing for the quantum revolution: What is the role of higher education?", Physical Review Physics Education Research 16, 020131 (2020), DOI: 10.1103/PhysRevPhysEducRes.16.02013
Quantum sensing, quantum networking and communication, and quantum computing have attracted significant attention recently, as these quantum technologies could offer significant advantages over existing technologies. In order to accelerate the commercialization of these quantum technologies, the workforce must be equipped with the necessary skills. Through a qualitative study of the quantum industry, we describe types of activities being carried out in the quantum industry, profile types of jobs that exist, and describe skills valued across the quantum industry and in each type of job. Current routes into the quantum industry are detailed, profiling the current role of higher education in training a quantum workforce.
 C. J. Kennedy, E. Oelker, J. M. Robinson, T. Bothwell, D. Kedar, W. R. Milner, G. E. Marti, A. Derevianko, and J. Ye, "Precision Metrology Meets Cosmology: Improved Constraints on on Ultralight Dark Matter from AtomCavity Frequency Comparisons", Phys. Rev. Lett. 125, 201302 (2020), DOI 10.1103/PhysRevLett.125.201302
We used three wellestablished quantum measurement techniques to set new limits on how strongly very lowmass candidates for hypothesized, but so far unobserved, "dark matter" interact with the atoms of regular matter familiar from the world around us. By using crosscomparisons of three measurement techniques, with their different sensitivities to different fundamental constants of Nature, we set tight limits on the properties of one hypothesized type of dark matter and suggest how to expand similar dark matter searches to higher mass. The success of this approach reinforces the trend of using optical light (in or near the visible range) instead of the traditional microwaves to measure time most accurately.
 K. Matsuda, L. De Marco, JR. Li, W.G. Tobias, G. Valtolina, G. Quéméner, J. Ye, "Resonant collisional shielding of reactive molecules using electric fields", Science, Vol. 370, Issue 6522, pp. 13241327 (2020), DOI: 10.1126/science.abe737
Ultracold gases of molecules offer a promising platform for new explorations in quantum science, but there's a catch: molecules can undergo rapid chemical reactions, severely limiting how long we can observe the interacting quantum system. In this work, we demonstrated a general method to "shield" molecules from chemical reactions by turning on an external electric field. At a particular electric field strength (the "shielding field"), our potassiumrubidium molecules strongly repelled each other at short distances, and as a result, the rate of chemical reactions was highly suppressed. Once shielded from chemical reactions, the molecules survived for ten times longer than at zero electric field, providing an excellent starting point for future experiments.
 S. Kelly, A. M. Rey, and J. Marino, "Effect of active photons on dynamical frustration in cavity QED", Physical Review Letters 126, 133603 (2021), 10.1103/PhysRevLett.126.133603
We studied the farfromequilibrium dynamical regimes of a manybody spinboson model with disordered couplings relevant for cavity QED and trapped ion experiments. Our study illustrated the resilience of glassylike dynamics in the presence of active photonic degrees of freedom, suggesting that disordered quantum manybody systems with resonant photons or phonons can display a rich diagram of nonequilibrium responses, with near future applications for quantum information science.
 R. J. LewisSwan, D. Barberena, J. R. K. Cline, D. Young, J.K. Thompson, and A. M. Rey, "CavityQED quantum simulator of dynamical phases of a BCS superconductor", Phys. Rev. Lett. 126, 173601 (2021), DOI 10.1103/PhysRevLett.126.173601
In a BCS superconductor electrons can overcome their electrostatic repulsion and manage to attract each other forming Cooper pairs. Superconductivity can naturally emerge by slowly modifying the temperature or pressure of special type of materials. However, it has been predicted that superconductivity can also emerge dynamically by abruptly changing the parameters of the system. So far only indirect evidence of these outofequilibrium phases exists in recent pumpprobe THz experiments. This work proposes a feasible way for the direct observation of dynamical superconductivity in a cavity QED setting where instead of Cooper pairs it is proposed to use atoms with two internal levels interacting via the exchange of photons in an optical cavity. This work demonstrates how the versatility and robustness of a cavityQED platform not only allows for the exhaustive study of the entire BCS phase diagram, but also enables experiments to study new dynamical phases in regimes inaccessible in real materials
 T. Bilitewski, L. De Marco, J. Li, K. Matsuda, W. Tobias, G. Valtolina, J. Ye, and A. M. Rey, "Dynamical generation of spin squeezing in ultracold dipolar molecules", Phys. Rev. Lett. 126, 113401 (2021). DOI 10.1103/PhysRevLett.126.113401
Creating a quantum gas of dipolar molecules brings new opportunities to explore exotic quantum phenomena. Exploring longrange interactions among molecules confined in reduced spatial dimensions, quantum correlations between rotations of individual molecules can be established, according to the theory model constructed on a realistic experimental platform. This correlation can be used to enhance metrological capabilities for field sensing
 M. Mamaev, I. Kimchi, R. Nandkishore, and A.M. Rey, "Tunable spin model generation in spinorbital coupled fermions in optical lattices", Physical Review Research 3, 013178 (2021). DOI 10.1103/PhysRevResearch.3.013178
We study the dynamical behavior of ultracold fermionic atoms loaded into an optical lattice under the presence of an effective magnetic flux, induced by spinorbitcoupled laser driving. At halffilling, the resulting system can emulate a variety of iconic spin1/2 models such as an Ising model, an XY model, a generic XXZ model with arbitrary anisotropy, or a collective oneaxis twisting model. The validity of these different spin models is examined across the parameter space of flux and driving strength. In addition, there is a parameter regime where the system exhibits chiral, persistent features in the longtime dynamics. We explore these properties and discuss the role played by the system's symmetries. We also discuss experimentally viable implementations.
 A. Chu, J. Will, J. Arlt, C. Klempt, and A. M. Rey, "Simulation of XXZ Spin Models using Sideband Transitions in Trapped Bosonic Gases", Physical Review Letters 125, 240504 (2020). DOI 10.1103/PhysRevLett.125.240504
We theoretically propose and experimentally demonstrate the use of motional sidebands in a trapped ensemble of ^{87}Rb atoms to engineer tunable longrange XXZ spin models. We benchmark our simulator by probing a ferromagnetic to paramagnetic dynamical phase transition in the LipkinMeshkovGlick model, a collective XXZ model plus additional transverse and longitudinal fields, via Rabi spectroscopy. We experimentally reconstruct the boundary between the dynamical phases, which is in good agreement with meanfield theoretical predictions. Our work introduces new possibilities in quantum simulation of anisotropic spinspin interactions and quantum metrology enhanced by manybody entanglement.
 R. J. LewisSwan, S.R. Muleady, and A. M. Rey, "Detecting outoftimeorder correlations via quasiadiabatic echoes as a tool to reveal quantum coherence in equilibrium quantum phase transitions", Physical Review Letters 125, 240605 (2020). DOI 10.1103/PhysRevLett.125.240605
We propose a new dynamical method to connect equilibrium quantum phase transitions and quantum coherence using outoftimeorder correlations (OTOCs). Adopting the iconic LipkinMeshkovGlick and transversefield Ising models as illustrative examples, we show that an abrupt change in coherence and entanglement of the ground state across a quantum phase transition is observable in the spectrum of multiple quantum coherence intensities, which are a special type of OTOC. We also develop a robust protocol to obtain the relevant OTOCs using quasiadiabatic quenches through the ground state phase diagram. Our scheme allows for the detection of OTOCs without time reversal of coherent dynamics, making it applicable and important for a broad range of current experiments where time reversal cannot be achieved by inverting the sign of the underlying Hamiltonian.
 M. H. MuñozArias, P. Poggi, and I. Deutsch, “Nonlinear dynamics and quantum chaos of a family of kicked pspin models”, Phys. Rev. E 103, 052212 (2021). DOI 10.1103/PhysRevE.103.052212
We introduce kicked pspin models describing a family of transverse Isinglike models for an ensemble of spin1/2 particles with alltoall pbody interaction terms occurring periodically in time as deltakicks. This is the natural generalization of the wellstudied quantum kicked top (p=2) [Haake, Kuś, and Scharf, Z. Phys. B 65, 381 (1987)]. We fully characterize the classical nonlinear dynamics of these models, including the transition to global Hamiltonian chaos. The classical analysis allows us to build a classification for this family of models, distinguishing between p = 2 and p > 2, and between models with odd and even p's. Quantum chaos in these models is characterized in both kinematic and dynamic signatures. For the latter, we show numerically that the growth rate of the outoftimeorder correlator is dictated by the classical Lyapunov exponent. Finally, we argue that the classification of these models constructed in the classical system applies to the quantum system as well.
 R.J. Fasano, Y.J. Chen, W.F. McGrew, W.J. Brand, R.W. Fox, and A.D. Ludlow, "Characterization and Suppression of Background Light Shifts in an Optical Lattice Clock", Phys. Rev. Applied 15, 044016 (2021), DOI: 10.1103/PhysRevApplied.15.044016
Experiments involving optical traps often require careful control of the ac Stark shifts induced by strong confining light fields. By carefully balancing light shifts between two atomic states of interest, optical traps at the magic wavelength have been especially effective at suppressing deleterious effects stemming from such shifts. Highlighting the power of this technique, optical clocks today exploit LambDicke confinement in magicwavelength optical traps, in some cases realizing shift cancelation at the ten parts per billion level. Theory and empirical measurements can be used at varying levels of precision to determine the magic wavelength where shift cancelation occurs. However, lasers exhibit background spectra from amplified spontaneous emission or other lasing modes that can easily contaminate measurement of the magic wavelength and its reproducibility in other experiments or conditions. Indeed, residual light shifts from laser background have plagued optical lattice clock measurements for years. In this work, we develop a simple theoretical model allowing prediction of light shifts from measured background spectra. We demonstrate good agreement between this model and measurements of the background light shift from an amplified diode laser in a Yb optical lattice clock. Additionally, we model and experimentally characterize the filtering effect of a volume Bragg grating bandpass filter, demonstrating that application of the filter can reduce background light shifts from amplified spontaneous emission well below the $10^{−18}$ fractional clock frequency level. This demonstration is corroborated by direct clock comparisons between a filtered amplified diode laser and a filtered titanium:sapphire laser.
 R. LewisSwan, S. R. Muleady, D. Barberena, J. J. Bollinger, and A. M. Rey, "Characterizing the dynamical phase diagram of the Dicke model via classical and quantum probes", Phys. Rev. Res. 3, L022020 (2021), DOI 10.1103/PhysRevResearch.3.L022020
We theoretically study the dynamical phase diagram of the Dicke model in both classical and quantum limits using large, experimentally relevant system sizes. Our analysis elucidates that the model features dynamical critical points that are strongly influenced by features of chaos and emergent integrability in the model. Moreover, our numerical calculations demonstrate that meanfield features of the dynamics remain valid in the exact quantum dynamics, but we also find that in regimes where quantum effects dominate signatures of the dynamical phases and chaos can persist in purely quantum metrics such as entanglement and correlations. Our predictions can be verified in current quantum simulators of the Dicke model including arrays of trapped ions.
 A. Cidrim, P. Orioli, C. Sanner, R. B. Hutson, J. Ye, R. Bachelard, and A. M. Rey, "Dipoledipole frequency shifts in multilevel atoms", Phys. Rev. Lett 127, 013401 (2021), DOI 10.1103/PhysRevLett.127.013401
Dipoledipole interactions lead to frequency shifts that are expected to limit the performance of nextgeneration atomic clocks. In this work, we compute dipolar frequency shifts accounting for the intrinsic atomic multilevel structure in standard Ramsey spectroscopy. When interrogating the transitions featuring the smallest ClebschGordan coefficients, we find that a simplified twolevel treatment becomes inappropriate, even in the presence of large Zeeman shifts. For these cases, we show a net suppression of dipolar frequency shifts and the emergence of dominant nonclassical effects for experimentally relevant parameters. Our findings are pertinent to current generations of optical lattice and optical tweezer clocks, opening a way to further increase their current accuracy, and thus their potential to probe fundamental and manybody physics.
 C. D. Marciniak, T. Feldker, I. Pogorelov, R. Kaubruegger, D. V. Vasilyev, R. van Bijnen, P. Schindler, P. Zoller, R. Blatt & T. Monz, "Optimal metrology with programmable quantum sensors", Nature volume 603, pages 604–609 (2022), DOI: 10.1038/s41586022044354
Quantum sensors are an established technology that has created new opportunities for precision sensing across the breadth of science. Using entanglement for quantum enhancement will allow us to construct the next generation of sensors that can approach the fundamental limits of precision allowed by quantum physics. However, determining how stateoftheart sensing platforms may be used to converge to these ultimate limits is an outstanding challenge. Here we merge concepts from the field of quantum information processing with metrology, and successfully implement experimentally a programmable quantum sensor operating close to the fundamental limits imposed by the laws of quantum mechanics. We achieve this by using lowdepth, parametrized quantum circuits implementing optimal input states and measurement operators for a sensing task on a trappedion experiment. With 26 ions, we approach the fundamental sensing limit up to a factor of 1.45 $\pm$ 0.01, outperforming conventional spinsqueezing with a factor of 1.87 $\pm$ 0.03. Our approach reduces the number of averages to reach a given Allan deviation by a factor of 1.59 $\pm$ 0.06 compared with traditional methods not using entanglementenabled protocols. We further perform ondevice quantumclassical feedback optimization to ‘selfcalibrate’ the programmable quantum sensor with comparable performance. This ability illustrates that this next generation of quantum sensor can be used without previous knowledge of the device or its noise environment.
 C. Hughes, D. Finke, D.A. German, C. Merzbacher, P. M. Vora, and H. J. Lewandowski, "Assessing the Needs of the Quantum Industry", IEEE Transactions on EducationVolume 65Issue 4, pp 592–601, DOI: 10.1109/TE.2022.3153841
Quantum information science and technology (QIST) has progressed significantly in the last decade, such that it is no longer solely in the domain of research labs, but is now beginning to be developed for, and applied in, industrial applications and products. With the emergence of this new quantum industry, a new workforce trained in QIST skills and knowledge is needed. To help support education and training of this workforce, universities and colleges require knowledge of the type of jobs available for their students and what skills and degrees are most relevant for those new jobs. Additionally, students need to know how to tailor their degrees to best align with the current needs of the quantum industry. We report on the results from a survey of 57 companies in the quantum industry, with the goal of elucidating the jobs, skills, and degrees that are relevant for this new workforce. We find a range of job opportunities from highly specific jobs, such as quantum algorithm developer and error correction scientist, to broader jobs categories within the business, software, and hardware sectors. These broader jobs require a range of skills, most of which are not quantum related. Further, except for the highly specific jobs, companies that responded to the survey are looking for a range of degree levels to fill these new positions, from bachelors to masters to PhDs. With this knowledge, students, instructors, and university administrators can make informed decisions about how to address the challenge of increasing the future quantum workforce.
 B. Li, J. Bartos, Y. Xie, and SW Huang, "Timemagnified photon counting with 550fs resolution", Optica 8, 1109 (2021) DOI 10.1364/OPTICA.420816
The authors demonstrate a quantum temporal magnifier that enables femtosecond timeresolved photon counting with closetounity efficiency for the first time. The new technology can benefit many research fields such as fluorescence lifetime microscopy, timeofflight imaging, lightinflight imaging, timegated Raman spectroscopy, and computational diffuse optical tomography.
 D. T. C. Allcock, W. C. Campbell, J. Chiaverini, I. L. Chuang, E. R. Hudson, I. D. Moore, A. Ransford, C. Roman, J. M. Sage, and D. J. Wineland, "omg Blueprint for Trapped Ion Quantum Computing with Metastable States", Appl. Phys. Lett. 119, 214002 (2021), DOI: 10.1063/5.0069544
Quantum computers, much like their classical counterparts, will likely benefit from flexible qubit encodings that can be matched to different tasks. For trapped ion quantum processors, a common way to access multiple encodings is to use multiple, cotrapped atomic species. Here, we outline an alternative approach that allows flexible encoding capabilities in singlespecies systems through the use of longlived metastable states as an effective, programmable second species. We describe the set of additional trapped ion primitives needed to enable this protocol and show that they are compatible with largescale systems that are already in operation.
 K. W. Lehnert, "Quantum enhanced metrology in the search for fundamental physical phenomena", to appear in "Quantum Information Machines; Lecture Notes of the Les Houches Summer School 2019", M. Devoret, B. Huard, and I. Pop editors, SciPost Phys. Lect. Notes 40 (2022), DOI: 10.21468/SciPostPhysLectNotes.40
These notes summarize lectures given at the 2019 Les Houches summer school on Quantum Information Machines. They describe and review an application of quantum metrology concepts to searches for ultralight dark matter. In particular, for ultralight dark matter that couples as a weak classical force to a laboratory harmonic oscillator, quantum squeezing benefits experiments in which the mass of the dark matter particle is unknown. This benefit is present even if the oscillatory dark matter signal is much more coherent than the harmonic oscillator that it couples to, as is the case for microwave frequency searches for dark matter axion particles.
 K. Wurtz, B. M. Brubaker, Y. Jiang, E. P. Ruddy, D. A. Palken, and K. W. Lehnert, "A cavity entanglement and state swapping method to accelerate the search for axion dark matter", PRX Quantum 2, 040350 (2021), DOI: 10.1103/PRXQuantum.2.040350
In cavitybased axion dark matter detectors, quantum noise remains a primary barrier to achieving the scan rate necessary for a comprehensive search of axion parameter space. Here we introduce a method of scan rate enhancement in which an axionsensitive cavity is coupled to an auxiliary resonant circuit through simultaneous twomode squeezing (entangling) and state swapping interactions. We show analytically that when combined, these interactions can amplify an axion signal before it becomes polluted by vacuum noise introduced by measurement. This internal amplification yields a wider bandwidth of axion sensitivity, increasing the rate at which the detector can search through frequency space. With interaction rates predicted by circuit simulations of this system, we show that this technique can increase the scan rate up to 15fold relative to the scan rate of a detector limited by vacuum noise.
 K. Gilmore, M. Affolter, R. J. LewisSwan, D. Barberena, E. Jordan, A. M. Rey, and J. J. Bollinger, "Quantumenhanced sensing of displacements and electric fields with twodimensional trappedion crystals", Science 373(6555), 673–678. (2021), DOI 10.1126/science.abi5226
Fully controllable ultracold atomic systems are creating opportunities for quantum sensing, yet demonstrating a quantum advantage in useful applications by harnessing entanglement remains a challenging task. Here, we realize a manybody quantumenhanced sensor to detect displacements and electric fields using a crystal of ~150 trapped ions. The centerofmass vibrational mode of the crystal serves as a highQ mechanical oscillator, and the collective electronic spin serves as the measurement device. By entangling the oscillator and collective spin and controlling the coherent dynamics via a manybody echo, a displacement is mapped into a spin rotation while avoiding quantum backaction and thermal noise. We achieve a sensitivity to displacements of 8.8 ± 0.4 decibels below the standard quantum limit and a sensitivity for measuring electric fields of 240 ± 10 nanovolts per meter in 1 second. Feasible improvements should enable the use of trapped ions in searches for dark matter.
 R. Kaubruegger, P. Silvi, C. Kokail, R. van Bijnen, A. M. Rey, J. Ye, A. M. Kaufman, and P. Zoller, "Variational spinsqueezing algorithms on programmable quantum sensors", Phys. Rev. Lett., 123, 260505 (2019), DOI 10.1103/PhysRevLett.123.260505
Arrays of atoms trapped in optical tweezers combine features of programmable analog quantum simulators with atomic quantum sensors. Here we propose variational quantum algorithms, tailored for tweezer arrays as programmable quantum sensors, capable of generating entangled states on demand for precision metrology. The scheme is designed to generate metrological enhancement by optimizing it in a feedback loop on the quantum device itself, thus preparing the best entangled states given the available quantum resources. We apply our ideas to the generation of spinsqueezed states on Sr atom tweezer arrays, where finiterange interactions are generated through Rydberg dressing. The complexity of experimental variational optimization of our quantum circuits is expected to scale favorably with system size. We numerically show our approach to be robust to noise, and surpassing known protocols.
 M. A. Perlin, D. Barberena, M. Mamaev, B. Sundar, R. J. LewisSwan, and A. M. Rey, "Engineering infiniterange SU(n) interactions with spinorbitcoupled fermions in an optical lattice", Phys. Rev. A. 105(2), 023326 (2022), DOI: 10.1103/PhysRevA.105.023326
We study multilevel fermions in an optical lattice described by the Hubbard model with on site SU(n)symmetric interactions. We show that in an appropriate parameter regime this system can be mapped onto a spin model with alltoall SU(n)symmetric couplings. Raman pulses that address internal spin states modify the atomic dispersion relation and induce spinorbit coupling, which can act as a synthetic inhomogeneous magnetic field that competes with the SU(n) exchange interactions. We investigate the meanfield dynamical phase diagram of the resulting model as a function of n and different initial configurations that are accessible with Raman pulses. Consistent with previous studies for n=2, we find that for some initial states the spin model exhibits two distinct dynamical phases that obey simple scaling relations with n. Moreover, for n${>}$2 we find that dynamical behavior can be highly sensitive to initial intraspin coherences. Our predictions are readily testable in current experiments with ultracold alkalineearth(like) atoms.
 T. Bilitewski, A. Pineiro Orioli, C. Sanner, L. Sonderhouse, R. B. Hutson, L. Yan, W. R. Milner, J. Ye, and A. M. Rey, "Disentangling Pauli blocking of atomic decay from cooperative radiation and atomic motion in a 2D Fermi gas", Phys. Rev. Lett. 128(9), 093001 (2022) DOI: 10.1103/physrevlett.128.093001
The observation of Pauli blocking of atomic spontaneous decay via direct measurements of the atomic population requires the use of longlived atomic gases where quantum statistics, atom recoil, and cooperative radiative processes are all relevant. We develop a theoretical framework capable of simultaneously accounting for all these effects in the manybody quantum degenerate regime. We apply it to atoms in a single 2D pancake or arrays of pancakes featuring an effective ${\Lambda}$ level structure (one excited and two degenerate ground states). We identify a parameter window in which a factor of 2 extension in the atomic lifetime clearly attributable to Pauli blocking should be experimentally observable in deeply degenerate gases with \sim ${10^3}$ atoms. We experimentally observe a suppressed excitedstate decay rate, fully consistent with the theory prediction of an enhanced excitedstate lifetime, on the ${^{1}S_{0}}  {^{3}P_{1}}$ transition in ${^{87}}$Sr atoms.
 A. Pineiro Orioli, J. K. Thompson, A. M. Rey, "Emergent dark states from superradiant dynamics in multilevel atoms in a cavity", Phys. Rev. X 12, 011054, (2022), DOI: 10.1103/PhysRevX.12.011054
When atoms are placed inside a cavity, the cavity light mediates collective interactions between atoms at arbitrary distances. For twolevel atoms, these collective interactions typically lead to superradiance—a phenomenon whereby atoms cooperate to emit light at an enhanced rate compared to a single atom. Here, we show that atoms with multiple internal levels instead give rise to dark subradiant states, where emission into the cavity is collectively suppressed. Because of their long lifetimes, subradiant states are useful for a wide range of quantum technological applications, but, so far, their actual creation has been challenging since they often require very short interparticle distances not easily achievable in current experiments. The physics of multilevel atoms inside cavities has remained severely underexplored. The main difficulty arises from the fact that multilevel atoms possess multiple transitions, which can couple to the two possible polarizations of light inside a cavity. However, we show that this additional layer of complexity allows multilevel atoms inside cavities to give rise to a plethora of entangled dark states, which are immune to cavity decay because of destructive interference between the light emitted by different internal transitions. These dark states are amenable to experimental observation since they naturally emerge during the superradiant decay path of initially excited atoms in a cavity: Atoms just get stuck in one of these dark states. Our findings open the door to the preparation of entangled dark states of matter through collective dissipation, which are useful for quantum sensing and quantum simulation.
 J. Huber, A. M. Rey, P. Rabi, "Realistic simulations of spin squeezing and cooperative coupling effects in large ensembles of interacting twolevel systems", Phys. Rev. A 105(1), 013716 (2022), DOI: 10.1103/PhysRevA.105.013716
We describe an efficient numerical method for simulating the dynamics of interacting spin ensembles in the presence of dephasing and decay. The method builds on the discrete truncated Wigner approximation for isolated systems, which combines the meanfield dynamics of a spin ensemble with a Monte Carlo sampling of discrete initial spin values to account for quantum correlations. Here we show how this approach can be generalized for dissipative spin systems by replacing the deterministic meanfield evolution by a stochastic process, which describes the decay of coherences and populations while preserving the length of each spin. We demonstrate the application of this technique for simulating nonclassical spinsqueezing effects or the dynamics and steady states of cavity QED models with ${10^5}$ interacting twolevel systems. This opens up the possibility to perform accurate realscale simulations of a diverse range of experiments in quantum optics or with solidstate spin ensembles under realistic laboratory conditions.
 A. Chu, P. He, J. K. Thompson, A. M. Rey, "Quantum enhanced cavity QED interferometer with partially delocalized atoms in lattices", Phys. Rev. Lett. 127, 210401 (2021), DOI: 10.1103/PhysRevLett.127.210401
We propose a quantum enhanced interferometric protocol for gravimetry and force sensing using cold atoms in an optical lattice supported by a standingwave cavity. By loading the atoms in partially delocalized WannierStark states, it is possible to cancel the undesirable inhomogeneities arising from the mismatch between the lattice and cavity fields and to generate spin squeezed states via a uniform oneaxis twisting model. The quantum enhanced sensitivity of the states is combined with the subsequent application of a compound pulse sequence that allows to separate atoms by several lattice sites. This, together with the capability to load small atomic clouds in the lattice at micrometric distances from a surface, make our setup ideal for sensing shortrange forces. We show that for arrays of $10^{4}$ atoms, our protocol can reduce the required averaging time by a factor of 10 compared to unentangled latticebased interferometers after accounting for primary sources of decoherence.
 C. Sanner, L. Sonderhouse, R. B. Hutson, L. Yan, W R. Milner, and J. Ye, "Pauli blocking of atomlight scattering", Science Vol 374, Issue 6570, pp. 979983 (2021), DOI: 10.1126/science.abh348
Transition rates between coupled states in a quantum system depend on the density of available final states. The radiative decay of an excited atomic state has been suppressed by reducing the density of electromagnetic vacuum modes near the atomic transition. Likewise, reducing the density of available momentum modes of the atomic motion when it is embedded inside a Fermi sea will suppress spontaneous emission and photon scattering rates. Here we report the experimental demonstration of suppressed light scattering in a quantum degenerate Fermi gas. We systematically measured the dependence of the suppression factor on the temperature and Fermi energy of a strontium quantum gas and achieved suppression of scattering rates by up to a factor of 2 compared with a thermal gas.
 S. Omanakuttan, A. Mitra, M. J. Martin, and I. H. Deutsch, "Quantum optimal control of tenlevel nuclear spin qudits in^{ 87}Sr", Phys. Rev. A 104, L060401 (2021), DOI: 10.1103/PhysRevA.104.L060401
We study the ability to implement unitary maps on states of the I = 9/2 nuclear spin in $^{87}$Sr, a d=10 dimensional (qudecimal) Hilbert space, using quantum optimal control. Through a combination of nuclear spin resonance and a tensor ac Stark shift, by solely modulating the phase of a radiofrequency magnetic field, the system is quantum controllable. Alkalineearthmetal atoms, such as $^{87}$Sr, have a very favorable figure of merit for such control due to narrow intercombination lines and the large hyperfine splitting in the excited states. We numerically study the quantum speed limit, optimal parameters, and the fidelity of arbitrary state preparation and full SU(10) maps, including the presence of decoherence due to optical pumping induced by the lightshifting laser. We also study the use of robust control to mitigate some dephasing due to inhomogeneities in the light shift. We find that with an rf Rabi frequency of $\Omega_{rf}$ and 0.5$\%$ inhomogeneity in the the light shift we can prepare an arbitrary Haarrandom state in a time $T = \frac{4.5\pi}{\Omega_{rf}}$ with average fidelity $$ = 0.9992, and an arbitrary Haarrandom SU(10) map in a time $T = \frac{24\pi}{\Omega_{rf}}$ with average fidelity $$ = 0.9923.
 S. B. Jäger, H. Liu, J. Cooper, M. J. Holland, "Collective emission of an atomic beam into an offresonant cavity mode”, Phys. Rev. A 104, 053705 (2021), DOI: 10.1103/PhysRevA.104.053705
We study the collective emission of a beam of atomic dipoles into an optical cavity. Our focus lies on the effect of a finite detuning between the atomic transition frequency and the cavity resonance frequency. By developing a theoretical description of the coupled atomcavity dynamics we analyze the stationary atomic configurations including a superradiant phase where the atoms undergo continuous monochromatic collective emission. In addition, we derive an analytical formula for the cavity pulling coefficient which characterizes the displacement of the emission frequency towards the cavity frequency. We find that the pulling is small if the cavity linewidth is much larger than the collective linewidth of the atomic beam. This regime is desired for building stable lasers because the emission frequency is robust against cavity length fluctuations. Furthermore, we investigate the stability of the atomic phases and compare our theoretical predictions with numerical results. Remarkably, we also find polychromatic emission regimes, where the spectrum has several frequency components while the light output is still superradiant.
 LY Chih, M. J. Holland, "Reinforcementlearningbased matterwave interferometer in a shaken optical lattice”, Physical Review Research 3, 033279 (2021), DOI: 10.1103/PhysRevResearch.3.033279
We demonstrate the design of a matterwave interferometer to measure acceleration in one dimension with high precision. The system we base this on consists of ultracold atoms in an optical lattice potential created by interfering laser beams. Our approach uses reinforcement learning, a branch of machine learning that generates the protocols needed to realize latticebased analogs of optical components including a beam splitter, a mirror, and a recombiner. The performance of these components is evaluated by comparison with their optical analogs. The interferometer's sensitivity to acceleration is quantitatively evaluated using a Bayesian statistical approach. We find the sensitivity to surpass that of standard Bragg interferometry, demonstrating the future potential for this design methodology.
 S. B. Jäger, H. Liu, J. Cooper, T. L. Nicholson, M. J. Holland, "Superradiant emission of a thermal atomic beam into an optical cavity”, Phys. Rev. A 104, 033711 (2021), DOI: 10.1103/PhysRevA.104.033711
We theoretically analyze the collective dynamics of a thermal beam of atomic dipoles that couple to a single mode when traversing an optical cavity. For this setup we derive a semiclassical model and determine the onset of superradiant emission and its stability. We derive analytical expressions for the linewidth of the emitted light and compare them with numerical simulations. In addition, we find and predict two different superradiant phases; a steadystate superradiant phase and a multicomponent superradiant phase. In the latter case we observe sidebands in the frequency spectrum that can be calculated using a stability analysis of the amplitude mode of the collective dipole. We show that both superradiant phases are robust against freespace spontaneous emission and T2 dephasing processes.
 A. Shankar, J. T. Reilly, S. B. Jäger, and M. J. Holland, "SubradianttoSubradiant Phase Transition in the Bad Cavity Laser”, Phys. Rev. Lett. 127, 073603 (2021), DOI: 10.1103/PhysRevLett.127.073603
We show that the onset of steadystate superradiance in a bad cavity laser is preceded by a dissipative phase transition between two distinct phases of steadystate subradiance. The transition is marked by a nonanalytic behavior of the cavity output power and the mean atomic inversion, as well as a discontinuity in the variance of the collective atomic inversion. In particular, for repump rates below a critical value, the cavity output power is strongly suppressed and does not increase with the atom number, while it scales linearly with atom number above this value. Remarkably, we find that the atoms are in a macroscopically entangled steady state near the critical region with a vanishing fraction of unentangled atoms in the large atom number limit.
 S. B. Jäger, H. Liu, A. Shankar, J. Cooper, M. J. Holland, "Regular and bistable steadystate superradiant phases of an atomic beam traversing an optical cavity”, Phys. Rev. A 103, 013720 (2021), DOI: 10.1103/PhysRevA.103.013720
We investigate the different photon emission regimes created by a preexcited and collimated atomic beam passing through a single mode of an optical cavity. In the regime where the cavity degrees of freedom can be adiabatically eliminated, we find that the atoms undergo superradiant emission when the collective linewidth exceeds the transittime broadening. We analyze the case where the atomic beam direction is slanted with respect to the cavity axis. For this situation, we find that a phase of continuous light emission similar to steadystate superradiance is established providing the tilt of the atomic beam is sufficiently small. However, if the atoms travel more than half a wavelength along the cavity axis during one transit time we predict a dynamical phase transition to a bistable superradiant regime. In this phase the atoms undergo collective spontaneous emission with a frequency that can be either blue or red detuned from the freespace atomic resonance. We analyze the different superradiant regimes and the quantum critical crossover boundaries. In particular we find the spectrum of the emitted light and show that the linewidth exhibits features of a critical scaling close to the phase boundaries.
 H. Liu, S. B. Jäger, X. Yu, S. Touzard, A. Shankar, M. J. Holland, T. L. Nicholson, "Rugged mhzlinewidth superradiant laser driven by a hot atomic beam”, Phys. Rev. Lett. 125, 253602 (2020), DOI: 10.1103/PhysRevLett.125.253602
We propose a new type of superradiant laser based on a hot atomic beam traversing an optical cavity. We show that the theoretical minimum linewidth and maximum power are competitive with the best ultracoherent clock lasers. Also, our system operates naturally in continuous wave mode, which has been elusive for superradiant lasers so far. Unlike existing ultracoherent lasers, our design is simple and rugged. This makes it a candidate for the first widely accessible ultracoherent laser, as well as the first to realize soughtafter applications of ultracoherent lasers in challenging environments.
 W.G. Tobias, K. Matsuda, JR. Li, C. Miller, A. N. Carroll, T. Bilitewski, A. M. Rey, J. Ye, "Reactions between layerresolved molecules mediated by dipolar spin exchange", Science, 375, p12991303 (2022) , DOI: 10.1126/science.abn8525
Microscopic control over polar molecules with tunable interactions enables the realization of distinct quantum phenomena. Using an electric field gradient, we demonstrated layerresolved state preparation and imaging of ultracold potassiumrubidium molecules confined to twodimensional planes in an optical lattice. The rotational coherence was maximized by rotating the electric field relative to the light polarization for stateinsensitive trapping. Spatially separated molecules in adjacent layers interact through dipolar spin exchange of rotational angular momentum; by adjusting these interactions, we regulated the local chemical reaction rate. The resonance width of the exchange process vastly exceeded the dipolar interaction energy, an effect attributed to thermal energy. This work realized precise control of interacting molecules, enabling electric field microscopy on subwavelength scales and allowing access to unexplored physics in twodimensional systems.
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 TW Hsu, W. Zhu, T. Thiele, M. O. Brown, S. B. Papp, A. Agrawal, and C. A. Regal, "Single atom trapping in a metasurface lens optical tweezer", PRX Quantum 3, 030316, DOI: 10.1103/PRXQuantum.3.030316
Optical metasurfaces of subwavelength pillars have provided new capabilities for the versatile definition of the amplitude, phase, and polarization of light. In this work, we demonstrate that an efficient dielectric metasurface lens can be used to trap and image single neutral atoms with a long working distance from the lens of 3 mm. We characterize the highnumericalaperture optical tweezers using the trapped atoms and compare with numerical computations of the metasurfacelens performance. We predict that future metasurfaces for atom trapping will be able to leverage multiple ongoing developments in metasurface design and enable multifunctional control in complex quantum information experiments with neutralatom arrays.
 M. O. Brown, S. R. Muleady, W. J. Dworschack, R. J. LewisSwan, A. M. Rey, O. RomeroIsart, and C. A. Regal, "TimeofFlight Quantum Tomography of Single Atom Motion", Nat. Phys. (2023), DOI: 10.1038/s41567022018908
A single particle trapped in a harmonic potential can exhibit rich motional quantum states within its highdimensional state space. Quantum characterization of motion is key, for example, in controlling or harnessing motion in trapped ion and atom systems or observing the quantum nature of the vibrational excitations of solidstate objects. Here we show that the direct measurement of position and momentum can be used for quantum tomography of motional states of a single trapped particle. We obtain the momentum of an atom in an optical tweezer via timeofflight measurements, which, combined with trap harmonic evolution, grants us access to all quadrature distributions. Starting with nonclassical motional states of a trapped neutral atom, we demonstrate the Wigner function negativity and coherence of nonstationary states. Our work will enable the characterization of the complex neutral atom motion that is of interest for quantum information and metrology, and for investigations of the quantum behaviour of massive levitated particles.
 A. Asfaw, A. Blais, K. R. Brown, J. Candelaria, C. Cantwell, L. D. Carr, J. Combes, D. M. Debroy, J. M. Donohue, S. E. Economou, E. Edwards, M. F. J. Fox, S. M. Girvin, A. Ho, H. M. Hurst, J. Zubin, B. R. Johnson, E. JohnstonHalperin, R. Joynt, E. Kapit, J. KleinSeetharaman, M. Laforest, H. J. Lewandowski, T. W. Lynn, C. R. H. McRae, C. Merzbacher, S. Michalakis, P. Narang, W. D. Oliver, J. Palsberg, D. P. Pappas, M. G. Raymer, D. J. Reilly, M. Saffman, T. A. Searles, J. H. Shapiro, and C. Singh, "Building a Quantum Engineering Undergraduate Program", IEEE Transactions on Education 123 (2022), DOI: 10.1109/TE.2022.3144943
Contribution: A roadmap is provided for building a quantum engineering education program to satisfy U.S. national and international workforce needs. Background: The rapidly growing quantum information science and engineering (QISE) industry will require both quantumaware and quantumproficient engineers at the bachelor's level. Research Question: What is the best way to provide a flexible framework that can be tailored for the full academic ecosystem? Methodology: A workshop of 480 QISE researchers from across academia, government, industry, and national laboratories was convened to draw on best practices; representative authors developed this roadmap. Findings: 1) For quantumaware engineers, design of a first quantum engineering course, accessible to all STEM students, is described; 2) for the education and training of quantumproficient engineers, both a quantum engineering minor accessible to all STEM majors, and a quantum track directly integrated into individual engineering majors are detailed, requiring only three to four newly developed courses complementing existing STEM classes; 3) a conceptual QISE course for implementation at any postsecondary institution, including community colleges and military schools, is delineated; 4) QISE presents extraordinary opportunities to work toward rectifying issues of inclusivity and equity that continue to be pervasive within engineering. A plan to do so is presented, as well as how quantum engineering education offers an excellent set of education research opportunities; and 5) a handson training plan on quantum hardware is outlined, a key component of any quantum engineering program, with a variety of technologies, including optics, atoms and ions, cryogenic and solidstate technologies, nanofabrication, and control and readout electronics.
 A. Derevianko, K. Gibble, L. Hollberg, N. R. Newbury, C. Oates, M. S. Safronova, L. C. Sinclair, N. Yu, "Fundamental Physics with a StateoftheArt Optical Clock in Space", Quantum Sci. Technol. 7, 044002 (2022), DOI: 10.1088/20589565/ac7df9
Recent advances in optical atomic clocks and optical time transfer have enabled new possibilities in precision metrology for both tests of fundamental physics and timing applications. Here we describe a space mission concept that would place a stateoftheart optical atomic clock in an eccentric orbit around Earth. A high stability laser link would connect the relative time, range, and velocity of the orbiting spacecraft to earthbound stations. The primary goal for this mission would be to test the gravitational redshift, a classical test of general relativity, with a sensitivity 30,000 times beyond current limits. Additional science objectives include other tests of relativity, enhanced searches for dark matter and drifts in fundamental constants, and establishing a high accuracy international time/geodesic reference.
 YD. Tsai, J. Eby, M. S. Safronova, "Direct detection of ultralight dark matter bound to the Sun with space quantum sensors", Nature Astronomy volume 7, pages 113–121 (2023, DOI: 10.1038/s41550022018336
Recent advances in quantum sensors, including atomic clocks, enable searches for a broad range of dark matter candidates. The question of the dark matter distribution in the Solar system critically affects the reach of dark matter direct detection experiments. Partly motivated by the NASA Deep Space Atomic Clock and the Parker Solar Probe, we show that space quantum sensors present new opportunities for ultralight dark matter searches, especially for dark matter states bound to the Sun. We show that space quantum sensors can probe unexplored parameter space of ultralight dark matter, covering theoretical relaxion targets motivated by naturalness and Higgs mixing. If a twoclock system were able to make measurements on the interior of the solar system, it could probe this highly sensitive region directly and set very strong constraints on the existence of such a boundstate halo in our solar system. We present sensitivity projections for spacebased probes of ultralight dark matter, which couples to electron, photon and gluon fields, based on current and future atomic, molecular and nuclear clocks.
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 Z. Lasner, A. Lunstad, C. Zhang, L. Cheng, J. M. Doyle, "Vibronic branching ratios for nearlyclosed rapid photon cycling of SrOH", Phys. Rev. A 106, L020801 – Published 3 August 2022, DOI: 10.1103/PhysRevA.106.L020801
The vibrational branching ratios of SrOH for radiative decay to the ground electronic state, ${X^{2}\Sigma^{+}}$, from the first two electronically excited states, ${A^{2}\Pi}$ and ${B^{2}\Sigma^{+}}$, are determined experimentally at the \sym ${10^{5}}$ level. The observed small branching ratios enable the design of a full, practical lasercooling scheme, including magnetooptical trapping and subDoppler laser cooling, with $> 10^{4}$ photon scatters per molecule. Ab initio calculations sensitive to weak vibronic transitions are performed to facilitate the experimental measurement and analysis, and show good agreement with experiment.
 A. Aeppli, A. Chu, T. Bothwell, C. J. Kennedy, D. Kedar, P. He, A. M. Rey, and J. Ye, "Hamiltonian engineering of spinorbit coupled fermions in a WannierStark optical lattice clock", Science Advances 8, eadc9242 (2022), DOI: 10.1126/sciadv.adc9242
Engineering a Hamiltonian system with tunable interactions provides opportunities to optimize performance for quantum sensing and explore emerging phenomena of manybody systems. An optical lattice clock based on partially delocalized WannierStark states in a gravitytilted shallow lattice supports superior quantum coherence and adjustable interactions via spinorbit coupling, thus presenting a powerful spin model realization. The relative strength of the onsite and offsite interactions can be tuned to achieve a zero density shift at a 'magic' lattice depth. This mechanism, together with a large number of atoms, enables the demonstration of the most stable atomic clock while minimizing a key systematic uncertainty related to atomic density. Interactions can also be maximized by driving offsite WannierStark transitions, realizing a ferromagnetic to paramagnetic dynamical phase transition.
 B. Sundar, D. Barberena, A. Piñeiro Orioli, A. Chu, J. K. Thompson, A. M. Rey, and R. J. LewisSwan, "Bosonic pair production and squeezing for optical phase measurements in longlived dipoles coupled to a cavity", Phys. Rev. Lett. 130, 113202, DOI: 10.1103/PhysRevLett.130.113202
We propose to simulate bosonic pair creation using large arrays of longlived dipoles with multilevel internal structure coupled to an undriven optical cavity. Entanglement between the atoms, generated by the exchange of virtual photons through a common cavity mode, grows exponentially fast and is described by twomode squeezing (TMS) of effective bosonic quadratures. The mapping between an effective bosonic model and the natural spin description of the dipoles allows us to realize the analog of optical homodyne measurements via straightforward global rotations and population measurements of the electronic states, and we propose to exploit this for quantumenhanced sensing of an optical phase (common and differential between two ensembles). We discuss a specific implementation based on Sr atoms and show that our sensing protocol is robust to sources of decoherence intrinsic to cavity platforms. Our proposal can open unique opportunities for the observation of continuous variable entanglement in atomic systems and associated applications in nextgeneration optical atomic clocks.
 C. Overstreet, P. Asenbaum, J. Curti, M. Kim, and M. A. Kasevich, “Observation of a Gravitational AharonovBohm Effect.” Science 375, no. 6577 (January 14, 2022): 226–29, DOI: 10.1126/science.abl7152
The AharonovBohm effect is a quantum mechanical effect in which a magnetic field affects the phase of an electron wave as it propagates along a wire. Atom interferometry exploits the wave characteristic of atoms to measure tiny differences in phase as they take different paths through the arms of an interferometer. Overstreet et al. split a cloud of cold rubidium atoms into two atomic wave packets about 25 centimeters apart and subjected one of the wave packets to gravitational interaction with a large mass (see the Perspective by Roura). The authors state that the observed phase shift is consistent with a gravitational AharonovBohm effect.
 B. K. Malia, Y. Wu, J. MartínezRincón, M. A. Kasevich, "Distributed quantum sensing with a modeentangled network of spinsqueezed atomic states", Nature 612, 661–665 (2022), DOI: 10.1038/s4158602205363z
Quantum sensors are used for precision timekeeping, field sensing, and quantum communication. Comparisons among a distributed network of these sensors are capable of, for example, synchronizing clocks at different locations. The performance of a sensor network is limited by technical challenges as well as the inherent noise associated with the quantum states used to realize the network. For networks with only local entanglement at each node, the noise performance of the network improves at best with square root of the number of nodes. Here, we demonstrate that nonlocal entanglement between network nodes offers better scaling with network size. A shared quantum nondemolition measurement entangles a clock network with up to four nodes. This network provides up to 4.5 dB better precision than one without nonlocal entanglement, and 11.6 dB improvement as compared to a network of sensors operating at the quantum projection noise limit. We demonstrate the generality of the approach with atomic clock and atomic interferometer protocols, in scientific and technologically relevant configurations optimized for intrinsically differential comparisons of sensor outputs.
 M. E. Kim, W. F. McGrew, N. V. Nardelli, E. R. Clements, Y. S. Hassan, X. Zhang, J. L. Valencia, H. Leopardi, D. B. Hume, T. M. Fortier, A. D. Ludlow, D. R. Leibrandt, “Improved interspecies optical clock comparisons through differential spectroscopy”, Nature Physics 19, 25 (2023), DOI: 10.1038/s41567022017947
Comparisons of highaccuracy optical atomic clocks1 are essential for precision tests of fundamental physics, relativistic geodesy and the anticipated redefinition of the second by the International System of Units. The scientific reach of these applications is restricted by the statistical precision of comparison measurements between clocks realized with different atomic species. The instability of individual clocks is limited by the finite coherence time of the optical local oscillator, which bounds the maximum atomic interrogation time. Here we experimentally demonstrate differential spectroscopy, a comparison protocol that enables interrogating times beyond the optical local oscillator coherence time. By phase coherently linking a zerodeadtime Yb optical lattice clock with an Al+ singleion clock via an optical frequency comb and performing synchronized Ramsey spectroscopy, we show an improvement in comparison instability relative to previous results of nearly an order of magnitude. This result represents one of the most stable interspecies clock comparisons to date.
 D. R. Leibrandt, S. G. Porsev, C. Cheung, M. S. Safronova, "Prospects of a thousandion Sn2+ Coulombcrystal clock with sub10^(−19) inaccuracy", (May, 2022), DOI: 10.48550/arXiv.2205.15484
We propose a manyion optical atomic clock based on threedimensional Coulomb crystals of order one thousand Sn$^{2+}$ ions confined in a linear RF Paul trap. Sn$^{2+}$ has a unique combination of features that is not available in previously considered ions: a $^{1}S_{0}$ $\leftrightarrow$ $^{3}P_{0}$ clock transition between two states with zero electronic and nuclear angular momentum (I = J = F = 0) making it immune to nonscalar perturbations, a negative differential polarizability making it possible to operate the trap in a manner such that the two dominant shifts for threedimensional ion crystals cancel each other, and a laseraccessible transition suitable for direct laser cooling and state readout. We present analytical calculations of the differential polarizability and other relevant atomic properties, as well as numerical calculations of the motion of ions in large Coulomb crystals, to estimate the achievable accuracy and precision of Sn$^{2+}$ Coulombcrystal clocks.
 E. D. Caldwell, L. C. Sinclair, N. R. Newbury, and JD Deschenes, "The Time Programmable Frequency Comb: Generation and Application to QuantumLimited DualComb Ranging", Nature 610, 667–673 (2022), DOI: 10.1038/s41586022052258
The classic selfreferenced frequency comb acts as an unrivaled ruler for precision optical metrology in both time and frequency. Two decades after its invention, the frequency comb is now used in numerous active sensing applications. Many of these applications, however, are limited by the tradeoffs inherent in the rigidity of the comb output and operate far from quantumlimited sensitivity. Here we demonstrate an agile programmable frequency comb where the pulse time and phase are digitally controlled with +/ 2 attosecond accuracy. This agility enables quantumlimited sensitivity in sensing applications since the programmable comb can be configured to coherently track weak returning pulse trains at the shotnoise limit. To highlight its capabilities, we use this programmable comb in a ranging system, reducing the detection threshold by ~5,000fold to enable nearly quantumlimited ranging at mean pulse photon number of 1/77 while retaining the full accuracy and precision of a rigid frequency comb. Beyond ranging and imaging, applications in time/frequency metrology, combbased spectroscopy, pumpprobe experiments, and compressive sensing should benefit from coherent control of the combpulse time and phase.
 X. Zhang, K. Beloy, Y. S. Hassan, W. F. McGrew, CC Chen, J. L. Siegel, T. Grogan, A. D. Ludlow, "Subrecoil clocktransition laser cooling enabling shallow optical lattice clocks", Phys. Rev. Lett. 129, 113202, DOI: 10.1103/PhysRevLett.129.113202
Laser cooling is a key ingredient for quantum control of atomic systems in a variety of settings. In divalent atoms, twostage Doppler cooling is typically used to bring atoms to the uK regime. Here, we implement a pulsed radial cooling scheme using the ultranarrow 1S03P0 clock transition in ytterbium to realize subrecoil temperatures, down to tens of nK. Together with sideband cooling along the onedimensional lattice axis, we efficiently prepare atoms in shallow lattices at an energy of 6 lattice recoils. Under these conditions key limits on lattice clock accuracy and instability are reduced, opening the door to dramatic improvements. Furthermore, tunneling shifts in the shallow lattice do not compromise clock accuracy at the 1019 level.
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 N. Hoghooghi, S. Xing, P. Chang, D. Lesko, A. Lind, G. Rieker, S. Diddams, "1GHz midinfrared frequency comb spanning 3 to 13 μm", Light Sci Appl 11, 264 (2022), DOI: 10.1038/s4137702200947w
Midinfrared (MIR) spectrometers are invaluable tools for molecular fingerprinting and hyperspectral imaging. Among the available spectroscopic approaches, GHz MIR dualcomb absorption spectrometers have the potential to simultaneously combine the highspeed, high spectral resolution, and broad optical bandwidth needed to accurately study complex, transient events in chemistry, combustion, and microscopy. However, such a spectrometer has not yet been demonstrated due to the lack of GHz MIR frequency combs with broad and full spectral coverage. Here, we introduce the first broadband MIR frequency comb laser platform at 1 GHz repetition rate that achieves spectral coverage from 3 to 13 {\mu}m. This frequency comb is based on a commercially available 1.56 {\mu}m modelocked laser, robust allfiber Er amplifiers and intrapulse difference frequency generation (IPDFG) of fewcycle pulses in \c{hi}(2) nonlinear crystals. When used in a dual comb spectroscopy (DCS) configuration, this source will simultaneously enable measurements with {\mu}s time resolution, 1 GHz (0.03 cm1) spectral point spacing and a full bandwidth of >5 THz (>166 cm1) anywhere within the MIR atmospheric windows. This represents a unique spectroscopic resource for characterizing fast and nonrepetitive events that are currently inaccessible with other sources.
 A. Mitra, S. Omanakuttan, M. J. Martin, G. W. Biedermann, I. H. Deutsch, "Quantum computing with subwavelength atomic arrays", Phys. Rev. A 109, 012613, DOI: 10.1103/PhysRevA.109.012613
Photonmediated interactions in subwavelength atomic arrays have numerous applications in quantum science. In this paper, we explore the potential of threelevel quantum emitters, or "impurities" embedded in a twodimensional atomic array to serve as a platform for quantum computation. By exploiting the altered behavior of impurities as a result of the induced dipoledipole interactions mediated by subwavelength arrays, we design and simulate a set of universal quantum gates consisting of the √iSWAP and singlequbit rotations. We demonstrate that these gates have very high fidelities due to the long atomic dipoledipole coherence times, as long as the atoms remain within a proximal range. Finally, we design and simulate quantum circuits leading to the generation of the maximally entangled twoqubit Bell states, as well as the entangled threequbit GreenbergerHorneZeilinger state. These findings establish subwavelength emitter arrays as an alternative platform for quantum computation and quantum simulation.
 R. A. Bravo, K. Najafi, X. Gao, S. F. Yelin, "Quantum reservoir computing using arrays of Rydberg atoms", PRX Quantum 3, 030325 (2022), DOI: 10.1103/PRXQuantum.3.030325
Quantum computing promises to provide machine learning with computational advantages. However, noisy intermediatescale quantum (NISQ) devices pose engineering challenges to realizing quantum machine learning (QML) advantages. Recently, a series of QML computational models inspired by the noisetolerant dynamics on the brain have emerged as a means to circumvent the hardware limitations of NISQ devices. In this article, we introduce a quantum version of a recurrent neural network (RNN), a wellknown model for neural circuits in the brain. Our quantum RNN (qRNN) makes use of the natural Hamiltonian dynamics of an ensemble of interacting spin1/2 particles as a means for computation. In the limit where the Hamiltonian is diagonal, the qRNN recovers the dynamics of the classical version. Beyond this limit, we observe that the quantum dynamics of the qRNN provide it quantum computational features that can aid it in computation. To this end, we study a qRNN based on arrays of Rydberg atoms, and show that the qRNN is indeed capable of replicating the learning of several cognitive tasks such as multitasking, decision making, and longterm memory by taking advantage of several key features of this platform such as interatomic species interactions, and quantum manybody scars.
 S. Ostermann, V. Walther, and S. F. Yelin, "Superglass formation in an atomic BEC with competing longrange interactions", Phys. Rev. Research 4, 023074 (2022), DOI: 10.1103/PhysRevResearch.4.023074
The complex dynamical phases of quantum systems are dictated by atomic interactions that usually evoke an emergent periodic order. Here, we study a quantum manybody system with two competing and substantially different longrange interaction potentials where the dynamical instability towards density order can give way to a disordered amorphous solid, which exhibits local density modulations but no longrange periodic order. We consider a twodimensional BoseEinstein condensate in the Rydbergdressing regime coupled to an optical standing wave resonator. The dynamic pattern formation in this system is governed by the competition between the two involved interaction potentials: repulsive softcore interactions arising due to Rydberg dressing and infiniterange sign changing interactions induced by the cavity photons. The amorphous phase is found when the two interaction potentials introduce incommensurate length scales. The dynamic formation of this peculiar phase can be attributed to frustration induced by the two competing interaction energies and length scales.
 T. L. Patti, J. Kossaifi, A. Anandkumar, S. F. Yelin, "Quantum Semidefinite Programming with the Hadamard Test and Approximate Amplitude Constraints", arXiv:2206.14999, DOI: 10.48550/arXiv.2206.14999
Semidefinite programs are optimization methods with a wide array of applications, such as approximating difficult combinatorial problems. We introduce a variational quantum algorithm for semidefinite programs that uses only n qubits, a constant number of circuit preparations, and ${O(n^{2})}$ expectation values in order to solve semidefinite programs with up to ${N=2^{n}}$ variables and ${M=2^{n}}$ constraints. Efficient optimization is achieved by encoding the objective matrix as a properly parameterized unitary conditioned on an auxilary qubit, a technique known as the Hadamard Test. The Hadamard Test enables us to optimize the objective function by estimating only a single expectation value of the ancilla qubit, rather than separately estimating exponentially many expectation values. Similarly, we illustrate that the semidefinite programming constraints can be effectively enforced by implementing a second Hadamard Test, as well as imposing ${\sim \frac{n^{2}}{2}}$ Pauli string amplitude constraints. We demonstrate the effectiveness of our protocol by devising an efficient quantum implementation of the GoemansWilliamson algorithm, which is a useful approximation for various NPhard problems, such as MaxCut. Our method exceeds the performance of analogous classical methods on a diverse subset of wellstudied MaxCut problems from the GSet library.
 J. Z. Lu, R. A. Bravo, K. Hou, G. A. Dagnew, S. F. Yelin, K. Najafi, "Learning quantum symmetries with interactive quantumclassical variational algorithms", arXiv:2206.11970, 10.48550/arXiv.2206.11970
A symmetry of a state is a unitary operator of which $ \Psi\rangle$ is an eigenvector. When ψ⟩ is an unknown state supplied by a blackbox oracle, the state's symmetries serve to characterize it, and often relegate much of the desired information about $ \Psi\rangle$. In this paper, we develop a variational hybrid quantumclassical learning scheme to systematically probe for symmetries of $ \Psi\rangle$ with no a priori assumptions about the state. This procedure can be used to learn various symmetries at the same time. In order to avoid relearning already known symmetries, we introduce an interactive protocol with a classical deep neural net. The classical net thereby regularizes against repetitive findings and allows our algorithm to terminate empirically with all possible symmetries found. Our scheme can be implemented efficiently on average with nonlocal SWAP gates; we also give a less efficient algorithm with only local operations, which may be more appropriate for current noisy quantum devices. We demonstrate our algorithm on representative families of states.
 B. Wu, G. P. Greve, C. Luo, J. K. Thompson, “Sitedependent selection of atoms for homogeneous atomcavity coupling,” arXiv:2104.01201 submitted to PRA, DOI: 10.48550/arXiv.2104.01201
We demonstrate a method to obtain homogeneous atomcavity coupling by selecting and keeping 87Rb atoms that are near maximally coupled to the cavity's standingwave mode. We select atoms by imposing an AC Stark shift on the ground state hyperfine microwave transition frequency with light injected into the cavity. We then induce a spin flip with microwaves that are resonant for atoms that are near maximally coupled to the cavity mode of interest, after which, we use radiation pressure forces to remove from the cavity all the atoms in the initial spin state. Achieving greater homogeneity in the atomcavity coupling will potentially enhance entanglement generation, intracavity driving of atomic transitions, cavityoptomechanics, and quantum simulations. This approach can easily be extended to other atomic species with microwave or optical transitions.
 G P. Greve, C. Luo, B. Wu, J. K. Thompson, “EntanglementEnhanced MatterWave Interferometry in a HighFinesse Cavity”, Nature 2022, 610 (7932), 472–477, DOI: 10.1038/s41586022051979
Entanglement is a fundamental resource that allows quantum sensors to surpass the standard quantum limit set by the quantum collapse of independent atoms. Collective cavityQED systems have succeeded in generating large amounts of directly observed entanglement involving the internal degrees of freedom of lasercooled atomic ensembles. Here we demonstrate cavityQED entanglement of external degrees of freedom to realize a matterwave interferometer of 700 atoms in which each individual atom falls freely under gravity and simultaneously traverses two paths through space while also entangled with the other atoms. We demonstrate both quantum nondemolition measurements and cavitymediated spin interactions for generating squeezed momentum states with directly observed metrological gain 3.4+1.1−0.9 dB and 2.5+0.6−0.6 dB below the standard quantum limit respectively. An entangled state is for the first time successfully injected into a MachZehnder lightpulse interferometer with 1.7+0.5−0.5 dB of directly observed metrological enhancement. Reducing the fundamental quantum source of imprecision provides a new resource that can be exploited to directly enhance measurement precision, bandwidth, and accuracy or operate at reduced size. These results also open a new path for combining particle delocalization and entanglement for inertial sensors, searches for new physics, particles, and fields, future advanced gravitational wave detectors, and accessing beyond meanfield quantum manybody physics.
 S. P. Kelly, J. K Thompson, A. M. Rey, J. Marino, “Resonant light enhances phase coherence in a cavity QED simulator of fermionic superfluidity”, Phys. Rev. Research 4, L042032 DOI: 10.1103/PhysRevResearch.4.L042032
Cavity QED experiments are natural hosts for nonequilibrium phases of matter supported by photonmediated interactions. In this work, we consider a cavity QED simulation of the BCS model of superfluidity, by studying regimes where the cavity photons act as dynamical degrees of freedom instead of mere mediators of the interaction via virtual processes. We find an enhancement of long time coherence following a quench whenever the cavity frequency is tuned into resonance with the atoms. We discuss how this is equivalent to enhancement of nonequilibrium superfluidity and highlight similarities to an analogous phenomena recently studied in solid state quantum optics. We also discuss the conditions for observing this enhanced resonant pairing in experiments by including the effect of photon losses and inhomogeneous coupling in our analysis.
 J. P. Bartolotta, S. B. Jäger, J. T. Reilly, M. A. Norcia, J. K. Thompson, G. Smith, M. J. Holland, “Entropy transfer from a quantum particle to a classical coherent light field”, Phys. Rev. Res. 4 013218, DOI: 10.1103/PhysRevResearch.4.013218
In the field of lightmatter interactions, it is often assumed that a classical light field that interacts with a quantum particle remains almost unchanged and thus contains nearly no information about the manipulated particles. To investigate the validity of this assumption, we develop and theoretically analyze a simple Gedanken experiment, which involves the interaction of a coherent state with a quantum particle in an optical cavity. We quantify the resulting alteration of the light field by calculating the fidelity of its initial and equilibrium states. Using Bayesian inference, we demonstrate the information transfer through photon statistics. In addition, we employ the concepts of quantum entropy and mutual information to quantify the entropy transfer from the particle to the light field. In the weak coupling limit, we validate the usually assumed negligible alteration of the light field and entropy transfer. In the strong coupling limit, however, we observe that the information of the initial particle state can be fully encoded in the light field, even for large photon numbers. Nevertheless, we show that spontaneous emission is a sufficient mechanism for removing the entropy initially stored in the particle. Our analysis provides a deeper understanding of the entropy exchange between quantum matter and classical light.
 T. Wilkason, M. Nantel, J. Rudolph, Y. Jiang, B. E. Garber, H. Swan, S. P. Carman, M. Abe, J. M. Hogan, "Atom Interferometry with Floquet Atom Optics", Phys. Rev. Lett. 129, 183202, DOI: 10.1103/PhysRevLett.129.183202
Floquet engineering offers a compelling approach for designing the time evolution of periodically driven systems. We implement a periodic atomlight coupling to realize Floquet atom optics on the strontium $^{1}S_{0}  ^{3}P_{1}$ transition. These atom optics reach pulse efficiencies above 99.4\% over a wide range of frequency offsets between light and atomic resonance, even under strong driving where this detuning is on the order of the Rabi frequency. Moreover, we use Floquet atom optics to compensate for differential Doppler shifts in large momentum transfer atom interferometers and achieve stateoftheart momentum separation in excess of 400 $\hbar k$. This technique can be applied to any twolevel system at arbitrary coupling strength, with broad application in coherent quantum control.
 S. BuckleyBonanno, S. Ostermann, O. RubiesBigorda, T. L. Patti, S. F. Yelin, "Optimized geometries for cooperative photon storage in an impurity coupled to a twodimensional atomic array", Phys. Rev. A 106, 053706 (2022), DOI: 10.1103/PhysRevA.106.053706
The collective modes of twodimensional ordered atomic arrays can modify the radiative environment of embedded atomic impurities. We analyze the role of the lattice geometry on the impurity's emission linewidth by comparing the effective impurity decay rate obtained for all noncentered Bravais lattices and an additional honeycomb lattice. We demonstrate that the lattice geometry plays a crucial role in determining the effective decay rate for the impurity. In particular, we find that the minimal effective decay rate appears in lattices where the number of the impurity's nearest neighbours is maximal and the number of distinct distances among nearest neighbours is minimal. We further show that, in the choice between interstitial and substitutional placement of the impurity, the former always wins by exhibiting a lower decay rate and longer photon storage. For interstitial placements, we determine the optimal impurity position in the lattice plane, which is not necessarily found in the center of the lattice plaquette.
 W. Zhong, X. Gao, S. F. Yelin, K. Najafi, "Manybody localized hidden Born machine", arXiv:2207.02346, 10.48550/arXiv.2207.02346
Born Machines are quantuminspired generative models that leverage the probabilistic nature of quantum states. Here, we present a new architecture called manybody localized (MBL) hidden Born machine that uses both MBL dynamics and hidden units as learning resources. We theoretically prove that MBL Born machines possess more expressive power than classical models, and the introduction of hidden units boosts its learning power. We numerically demonstrate that the MBL hidden Born machine is capable of learning a toy dataset consisting of patterns of MNIST handwritten digits, quantum data obtained from quantum manybody states, and nonlocal parity data. In order to understand the mechanism behind learning, we track physical quantities such as von Neumann entanglement entropy and Hamming distance during learning, and compare the learning outcomes in the MBL, thermal, and Anderson localized phases. We show that the superior learning power of the MBL phase relies importantly on both localization and interaction. Our architecture and algorithm provide novel strategies of utilizing quantum manybody systems as learning resources, and reveal a powerful connection between disorder, interaction, and learning in quantum systems.
 J. T. Reilly, S. B. Jäger, J. Cooper, M. J. Holland, "Adiabatic Control of DecoherenceFreeSubspaces in an Open Collective System", Phys. Rev. A 106, 023703 (2022), DOI: 10.1103/PhysRevA.106.023703
We propose a method to adiabatically control an atomic ensemble using a decoherencefree subspace (DFS) within a dissipative cavity. We can engineer a specific eigenstate of the system's Lindblad jump operators by injecting a field into the cavity which deconstructively interferes with the emission amplitude of the ensemble. In contrast to previous adiabatic DFS proposals, our scheme creates a DFS in the presence of collective decoherence. We therefore have the ability to engineer states that have high multiparticle entanglements which may be exploited for quantum information science or metrology. We further demonstrate a more optimized driving scheme that utilizes the knowledge of possible diabatic evolution gained from the socalled adiabatic criteria. This allows us to evolve to a desired state with exceptionally high fidelity on a time scale that does not depend on the number of atoms in the ensemble. By engineering the DFS eigenstate adiabatically, our method allows for faster state preparation than previous schemes that rely on damping into a desired state solely using dissipation.
 S. B. Jäger, T. Schmit, G. Morigi, M. J. Holland, R. Betzholz, "Lindblad master equations for quantum systems coupled to dissipative bosonic modes", Phys. Rev. Lett. 129, 063601, DOI: 10.1103/PhysRevLett.129.063601
We present a general approach to derive Lindblad master equations for a subsystem whose dynamics is coupled to dissipative bosonic modes. The derivation relies on a SchriefferWolff transformation which allows to eliminate the bosonic degrees of freedom after selfconsistently determining their state as a function of the coupled quantum system. We apply this formalism to the dissipative Dicke model and derive a Lindblad master equation for the atomic spins, which includes the coherent and dissipative interactions mediated by the bosonic mode. This master equation accurately predicts the Dicke phase transition and gives the correct steady state. In addition, we compare the dynamics using exact diagonalization and numerical integration of the master equation with the predictions of semiclassical trajectories. We finally test the performance of our formalism by studying the relaxation of a NOON state and show that the dynamics captures quantum metastability beyond the meanfield approximation.
 J. D. Wilson, S. B. Jäger, J. T. Reilly, A. Shankar, M.L. Chiofalo, M. J. Holland, "Beyond oneaxis twisting: Simultaneous spinmomentum squeezing", submitted to Phys. Rev. A (2022); Phys. Rev. A 106, 043711, DOI: 10.1103/PhysRevA.106.043711
The creation and manipulation of quantum entanglement is central to improving precision measurements. A principal method of generating entanglement for use in atom interferometry is the process of spin squeezing whereupon the states become more sensitive to SU(2) rotations. One possibility to generate this entanglement is provided by oneaxis twisting (OAT), where a manyparticle entangled state of one degree of freedom is generated by a nonlinear Hamiltonian. We introduce a novel method which goes beyond OAT to create squeezing and entanglement across two distinct degrees of freedom. We present our work in the specific physical context of a system consisting of collective atomic energy levels and discrete collective momentum states, but also consider other possible realizations. Our system uses a nonlinear Hamiltonian to generate dynamics in SU(4), thereby creating the opportunity for dynamics not possible in typical SU(2) oneaxis twisting. This leads to three axes undergoing twisting due to the two degrees of freedom and their entanglement, with the resulting potential for a more rich context of quantum entanglement. The states prepared in this system are potentially more versatile for use in multiparameter or auxiliary measurement schemes than those prepared by standard spin squeezing.
 G. W. Harmon, J. T. Reilly, M. J. Holland, S. B. Jäger, "Meanfield Floquet theory for a threelevel coldatom laser", Phys. Rev. A 106, 013706 (2022), DOI: 10.1103/PhysRevA.106.013706
We present a theoretical description for a lasing scheme for atoms with three internal levels in a V configuration and interacting with an optical cavity. The use of a Vlevel system allows for an efficient closed lasing cycle to be sustained on a dipoleforbidden transition without the need for incoherent repumping. This is made possible by utilizing an additional dipoleallowed transition. We determine the lasing threshold and emission frequency by performing a stability analysis of the nonlasing solution. In the lasing regime, we use a meanfield Floquet method (MFFM) to calculate the lasing intensity and emission frequency. This MFFM predicts the lasing transition to be accompanied by the breaking of a continuous U(1) symmetry in a single Fourier component of the total field. In addition, we use the MFFM to derive bistable lasing and nonlasing solutions that highlight the nonlinear nature of this system. We then test the bistability by studying hysteresis when slowly ramping external parameters across the threshold and back. Furthermore, we also compare our meanfield results to a secondorder cumulant approach. The work provides simple methods for understanding complex physics that occur in cold atom lasers with narrow line transitions.
 N. Schine, A. W. Young, W. Eckner, M. Martin, A. M. Kaufman, "LongLived Bell states in an array of optical clock qubits", Nature Physics volume 18, pages 1067–1073 (2022), DOI: 10.1038/s4156702201678w
The generation of longlived entanglement on an optical clock transition is a key requirement to unlocking the promise of quantum metrology. Arrays of neutral atoms constitute a capable quantum platform for accessing such physics, where Rydbergbased interactions may generate entanglement between individually controlled and resolved atoms. To this end, we leverage the programmable state preparation afforded by optical tweezers along with the efficient strong confinement of a 3d optical lattice to prepare an ensemble of strontium atom pairs in their motional ground state. We engineer global singlequbit gates on the optical clock transition and twoqubit entangling gates via adiabatic Rydberg dressing, enabling the generation of Bell states, $ \Psi \rangle=\frac{1}{\sqrt{2}}( gg \rangle + i ee \rangle)$, with a fidelity of F =92.8(2.0)\%. For use in quantum metrology, it is furthermore critical that the resulting entanglement be long lived; we find that the coherence of the Bell state has a lifetime of $\tau_{bc}$ = 4.2(6) s via parity correlations and simultaneous comparisons between entangled and unentangled ensembles. Such Bell states can be useful for enhancing metrological stability and bandwidth. Further rearrangement of hundreds of atoms into arbitrary configurations using optical tweezers will enable implementation of manyqubit gates and cluster state generation, as well as explorations of the transverse field Ising model and Hubbard models with entangled or finiterangeinteracting tunnellers.
 S. Colombo, E. PedrozoPenafiel, A. Adiyatullin, Z. Li, E. Mendez, C. Shu, and V. Vuletić, "Timereversalbased quantum metrology with manybody entangled states", Nature Phys. (2022); DOI: 10.1038/s41567022016535
Linear quantum measurements with independent particles are bounded by the standard quantum limit, which limits the precision achievable in estimating unknown phase parameters. The standard quantum limit can be overcome by entangling the particles, but the sensitivity is often limited by the final state readout, especially for complex entangled manybody states with nonGaussian probability distributions. Here, by implementing an effective timereversal protocol in an optically engineered manybody spin Hamiltonian, we demonstrate a quantum measurement with nonGaussian states with performance beyond the limit of the readout scheme. This signal amplification through a timereversed interaction achieves the greatest phase sensitivity improvement beyond the standard quantum limit demonstrated to date in any full Ramsey interferometer. These results open the field of robust timereversalbased measurement protocols offering precision not too far from the Heisenberg limit. Potential applications include quantum sensors that operate at finite bandwidth, and the principle we demonstrate may also advance areas such as quantum engineering, quantum measurements and the search for new physics using opticaltransition atomic clocks.
 N. Irtija, J. Plusquellic, E. E. Tsiropoulou, J. Goldberg, D. Lobser, and D. Stick, "Design and analysis of digital communication within an SoCbased control system for trappedion quantum computing", IEEE Transactions on Quantum Engineering, vol. 4, pp. 124, 2023, Art no. 5500124, DOI: 10.1109/TQE.2023.3238670
Electronic control systems used for quantum computing have become increasingly complex as multiple qubit technologies employ larger numbers of qubits with higher fidelity targets. Whereas the control systems for different technologies share some similarities, parameters like pulse duration, throughput, realtime feedback, and latency requirements vary widely depending on the qubit type. In this paper, we evaluate the performance of modern SystemonChip (SoC) architectures in meeting the control demands associated with performing quantum gates on trappedion qubits, particularly focusing on communication within the SoC. A principal focus of this paper is the data transfer latency and throughput of several highspeed onchip mechanisms on Xilinx multiprocessor SoCs, including those that utilize direct memory access (DMA). They are measured and evaluated to determine an upper bound on the time required to reconfigure a gate parameter. Worstcase and averagecase bandwidth requirements for a custom gate sequencer core are compared with the experimental results. The lowestvariability, highestthroughput datatransfer mechanism is DMA between the realtime processing unit (RPU) and the PL, where bandwidths up to 19.2 GB/s are possible. For context, this enables reconfiguration of qubit gates in less than 2\mics\!, comparable to the fastest gate time. Though this paper focuses on trappedion control systems, the gate abstraction scheme and measured communication rates are applicable to a broad range of quantum computing technologies.
 M. Nie, B. Li, K. Jia, Y. Xie, J. Yan, S.N. Zhu, Z. Xie, and S.W. Huang, "Dissipative soliton generation and realtime dynamics in microresonatorfiltered fiber lasers", Light Sci Appl 11, 296 (2022), DOI: 10.1038/s4137702200998z
Optical frequency combs in microresonators (microcombs) have a wide range of applications in science and technology, due to its compact size and access to considerably larger comb spacing. Despite recent successes, the problems of selfstarting, high mode efficiency as well as high output power have not been fully addressed for conventional soliton microcombs. Recent demonstration of laser cavity soliton microcombs by nesting a microresonator into a fiber cavity, shows great potential to solve the problems. Here we study the dissipative soliton generation and interaction dynamics in a microresonatorfiltered fiber laser in both theory and experiment. We bring theoretical insight into the modelocking principle, discuss the parameters effect on soliton properties, and provide experimental guidelines for broadband soliton generation. We predict chirped bright dissipative soliton with flattop spectral envelope in microresonators with normal dispersion, which is fundamentally forbidden for the externally driven case. Furthermore, we experimentally achieve soliton microcombs with large bandwidth of ~10 nm and high mode efficiency of 90.7%. Finally, by taking advantage of an ultrahighspeed time magnifier, we study the realtime soliton formation and interaction dynamics and experimentally observe soliton Newton’s cradle. Our study will benefit the design of the novel, highefficiency and selfstarting microcombs for realworld applications.
 S. Z. Ahmed, C. A. Weidner, J. H. M. Jensen, J. F. Sherson, and H. J. Lewandowski, "Student use of a quantum simulation and visualization tool", Eur. J. Phys. 43 065703, DOI: 10.1088/13616404/ac93c7
Knowledge of quantum mechanical systems is becoming more important for many science and engineering students who are looking to join the emerging quantum workforce. To better prepare a wide range of students for these careers, we must seek to develop new tools to enhance our education in quantum topics. We present initial studies on the use of one of these such tools, Quantum Composer, a 1D quantum simulation and visualization tool developed for education and research purposes. In particular, we conducted five thinkaloud interviews with students who worked through an exercise using Quantum Composer that focused on the statics and dynamics of quantum states in a single harmonic well system. Our results show that Quantum Composer helps students to obtain the correct answers to the questions posed, but additional support is needed to facilitate the development of student reasoning behind these answers. We also show that students are able to focus only on the relevant features of Quantum Composer to achieve the task.
 J.R. Li, K. Matsuda, C. Miller, A. N. Carroll, W. G. Tobias, J. S. Higgins, J. Ye, "Tunable itinerant spin dynamics with polar molecules", Nature 614, 70–74 (2023), DOI: 10.1038/s41586022054792
Strongly interacting spins underlie many intriguing phenomena and applications ranging from quantum magnetism and spin transport to precision quantum sensing and quantum information processing. An interacting spin system with high controllability is desired in order to understand these complex phenomena. Here, we demonstrate tunable itinerant spin dynamics enabled by dipolar interactions using a gas of potassiumrubidium molecules confined to twodimensional planes, where the spin1/2 is encoded in the molecular rotational levels. The dipolar interaction gives rise to a shift of the rotational transition frequency and a collisionlimited Ramsey contrast decay that emerges from the coupled spin and motion. Both the Ising and spin exchange interactions are precisely tuned by varying the strength and orientation of an electric field, as well as the internal molecular state. This full tunability enables both static and dynamical control of the spin Hamiltonian, allowing reversal of the coherent spin dynamics. Our work establishes an interacting spin platform that allows for exploration of manybody spin dynamics and spinmotion physics utilizing the strong, tunable dipolar interaction.
 C. Kiehl, D. Wagner, TW. Hsu, S. Knappe, C. A. Regal, T. Thiele, "Coherence of Rabi oscillations with spin exchange", Physical Review Research 5, L012002 (2023), DOI: 10.1103/PhysRevResearch.5.L012002
Rabi measurements in atomic vapor cells are of current interest in a range of microwave imaging and sensing experiments, but are increasingly in a parameter space outside of theoretical studies of coherence defined by spin exchange collisions. Here, we study the coherence of Rabi oscillations in vapor cells by employing continuous nondestructive readout of the hyperfine manifold of {^87}Rb using Faraday rotation. We develop a full model for spinexchange coherence for hyperfine transitions that takes into account a nonstatic population distribution. In this regime, Rabi oscillations exhibit nontrivial timedomain signals that allow verification of vaporcell parameters. We find excellent agreement between theory and experiment, which will aid in benchmarking sensitivities of Rabi measurement applications.
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 A. M. Polloreno, J. L. Beckey, J. Levin, A. Shlosberg, J. K. Thompson, M. FossFeig, D. Hayes, G. Smith, "Opportunities and Limitations in Broadband Sensing", Phys. Rev. Applied 19, 014029, DOI: 10.1103/PhysRevApplied.19.014029
We consider estimating the magnitude of a monochromatic AC signal that couples to a twolevel sensor. For any detection protocol, the precision achieved depends on the signal's frequency and can be quantified by the quantum Fisher information. To study limitations in broadband sensing, we introduce the integrated quantum Fisher information and derive inequality bounds that embody fundamental tradeoffs in any sensing protocol. These inequalities show that sensitivity in one frequency range must come at a cost of reduced sensitivity elsewhere. For many protocols, including those with small phase accumulation and those consisting of $\pi$pulses, we find the integrated Fisher information scales linearly with T. We also find protocols with substantial phase accumulation can have integrated QFI that grows quadratically with T, which is optimal. These protocols may allow the very rapid detection of a signal with unknown frequency over a very wide bandwidth.
 A. Chu, A. P. Orioli, D. Barberena, J. K. Thompson, A. M. Rey, "Photonmediated correlated hopping in a synthetic ladder" Phys. Rev. Research 5, L022034, DOI: 10.1103/PhysRevResearch.5.L022034
We propose a new direction in quantum simulation that uses multilevel atoms in an optical cavity as a toolbox to engineer new types of bosonic models featuring correlated hopping processes in a synthetic ladder spanned by atomic ground states. The underlying mechanisms responsible for correlated hopping are collective cavitymediated interactions that dress a manifold of excited levels in the far detuned limit. By weakly coupling the ground state levels to these dressed states using two laser drives with appropriate detunings, one can engineer correlated hopping processes while suppressing undesired singleparticle and collective shifts of the ground state levels. We discuss the rich manybody dynamics that can be realized in the synthetic ladder including pair production processes, chiral transport and lightcone correlation spreading. The latter illustrates that an effective notion of locality can be engineered in a system with fully collective interactions.
 J. R. K. Cline, V. M. Schäfer, Z. Niu, D. J. Young, T. H. Yoon, J. K. Thompson, "Continuous collective strong coupling between atoms and a high finesse optical cavity", arXiv:2211.00158v1, DOI: 10.48550/arXiv.2211.00158
We demonstrate continuous loading of strontium atoms into a high finesse ring cavity and observe continuous strong collective coupling in the form of a vacuum Rabi splitting between the atoms and the cavity on the 7.5 kHz transition $^{1}S_{0}$ to ${^{3}P_{1}$. The atoms are loaded into the cavity from a 3D narrow linewidth molasses, thus avoiding large magnetic field gradients and associated broadening of transition frequencies. The ring cavity allows us to realize a deterministic conveyor belt to transport atoms away from the loading region where the laser cooling beams lead to broadening of the strontium clock transition. We trap up to $10^{6}$ atoms in an intracavity 813 nm lattice in the LambDicke regime, and transport the atoms along the cavity axis. This work opens the path to the creation of a continuous wave superradiant laser with millihertz linewidth enabling searches for new physics and the use of highprecision optical frequency references outside of low vibration laboratory environments.
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 I.D. Moore, W.C. Campbell, E.R. Hudson, M.J. Boguslawski, D.J. Wineland, D.T.C. Allcock, "Photon scattering errors during stimulated Raman transitions in trappedion qubits", Phys. Rev. A 107, 032413, DOI: 10.1103/PhysRevA.107.032413
We study photon scattering errors in stimulated Raman driven quantum logic gates. For certain parameter regimes, we find that previous simplified models of the process significantly overestimate the gate error rate due to photon scattering. This overestimate is shown to be due to previous models neglecting the detuning dependence of the scattered photon frequency and LambDicke parameter, a second scattering process, interference effects on scattering rates to metastable manifolds, and the counterrotating contribution to the Raman transition rate. The resulting improved model shows that there is no fundamental limit on gate error due to photon scattering for electronic groundstate qubits in commonly used trappedion species when the Raman laser beams are red detuned from the main optical transition. Additionally, photon scattering errors are studied for qubits encoded in the metastable ${D}_{5/2}$ manifold, showing that gate errors below ${10}^{\ensuremath{}4}$ are achievable for all commonly used trapped ions.
 J.M. Robinson, M. Miklos, Y.M. Tso, C.J. Kennedy, T. Bothwell, D. Kedar, J.K. Thompson, J. Ye, "Direct Comparison of Two SpinSqueezed Optical Clock Ensembles at the 10−17 Level", Nat. Phys. 2024, 20 (2), 208–213, DOI: 10.1038/s41567023023101
Building scalable quantum systems that demonstrate genuine performance enhancement based on entanglement is a major scientific goal for fields including computing, networking, simulations, and metrology. The tremendous challenge arises from the fragility of entanglement in increasingly larger sized quantum systems. Optical atomic clocks utilizing a large number of atoms have pushed the frontier of measurement science, building on precise engineering of quantum states and control of atomic interactions. However, today's stateoftheart optical atomic clocks are limited by the quantum projection noise (QPN) defined by many uncorrelated atoms. Pioneering work on producing spin squeezed states of atoms has shown a path towards integrating entanglement into the best performing clocks. However, to directly demonstrate advantage of quantum entanglement in a working clock we must prevent backaction effects that degrade quantum coherence and introduce uncontrolled perturbations, as well as minimize the influence of technical noise arising from the interrogating clock laser. Here we present a new optical clock platform integrated with collective strongcoupling cavity QED for quantum nondemolition (QND) measurement. Optimizing the competition between spin measurement precision and loss of coherence, we measure a Wineland parameter of 1.8(7) dB for $1.9x10^{4}$ atoms, thus verifying the presence of entanglement. Furthermore, a moving lattice allows the cavity to individually address two independent subensembles, enabling us to spin squeeze two clock ensembles successively and compare their performance. This differential comparison between the two squeezed clocks directly verifies enhanced clock stability of 2.0(3) dB below QPN, and 0.6(3) dB above the standard quantum limit (SQL), at the measurement precision level of $10^{17}$, without subtracting any technical noise contributions.
 W. J. Eckner, N. D. Oppong, A. Cao, A. W. Young, W. R. Milner, J. M. Robinson, J. Ye, and A. M. Kaufman, "Realizing spin squeezing with Rydberg interactions in a programmable optical clock", Nature 621, 734–739 (2023), DOI: 10.1038/s41586023063606
Neutralatom arrays trapped in optical potentials are a powerful platform for studying quantum physics, combining precise singleparticle control and detection with a range of tunable entangling interactions. For example, these capabilities have been leveraged for stateoftheart frequency metrology as well as microscopic studies of entangled manyparticle states. In this work, we combine these applications to realize spin squeezing  a widely studied operation for producing metrologically useful entanglement  in an optical atomic clock based on a programmable array of interacting optical qubits. In this first demonstration of Rydbergmediated squeezing with a neutralatom optical clock, we generate states that have almost 4 dB of metrological gain. Additionally, we perform a synchronous frequency comparison between independent squeezed states and observe a fractional frequency stability of 1.087(1) x $10^{15}$ at onesecond averaging time, which is 1.94(1) dB below the standard quantum limit, and reaches a fractional precision at the $10^{17}$ level during a halfhour measurement. We further leverage the programmable control afforded by optical tweezer arrays to apply local phase shifts in order to explore spin squeezing in measurements that operate beyond the relative coherence time with the optical local oscillator. The realization of this spinsqueezing protocol in a programmable atomarray clock opens the door to a wide range of quantuminformation inspired techniques for optimal phase estimation and Heisenberglimited optical atomic clocks.
 Y. Jiang, E.P. Ruddy, K.O. Quinlan, M. Malnou, N.E. Frattini, and K.W. Lehnert, “Accelerated Weak Signal Search Using Mode Entanglement and State Swapping,” PRX Quantum 4, 020302 (2023), DOI: 10.1103/PRXQuantum.4.020302
Quantum fluctuations constitute the primary noise barrier limiting cavitybased axiondarkmatter searches. In an experiment designed to mimic a real axion search, we employ a quantum enhanced sensing technique to detect a synthetic axionlike microwave tone at an unknown frequency weakly coupled to a resonator, demonstrating a factorof5.6 acceleration relative to a quantum limited search for the same tone. This speedup is achieved by dynamically coupling the resonator mode to a second (readout) mode with balanced swapping and twomode squeezing interactions, which results in both visibilitybandwidth and peakvisibility increase. A small fractional imbalance between the two interaction rates yields further scanrate enhancement and we demonstrate that an eightfold acceleration can be achieved.
 Z. Zhao, E. Gurra, E. I. Rosenthal, L. R. Vale, G. C. Hilton, K. W. Lehnert, “Integrating planar circuits with superconducting 3D microwave cavities using tunable lowloss couplers", Applied Physics Letters 123 (1), 014001 (2023), DOI: 10.1063/5.0153936
We design and test a lowloss interface between superconducting 3dimensional microwave cavities and 2dimensional circuits, where the coupling rate is highly tunable. This interface seamlessly integrates a magnetic antenna and a Josephson junction based coupling element with a cavity, and we demonstrate that the introduced loss from this integration only limits the quality factor to 4.5 million. The cavity external coupling rate can then be tuned from negligibly small to over 3 orders of magnitude larger than the internal loss rate with a characteristic time of 3.2 ns. This switching speed does not impose additional limits on the coupling rate because it is much faster than the coupling rate. Moreover, the coupler can be controlled by baseband signals to avoid interference with microwave signals near the cavity or qubit frequencies. Finally, the coupling element introduces a 0.04 Hz/photon selfKerr nonlinearity to the cavity, remaining linear in high photon number operations.
 M. H. MuñozArias, I. H. Deutsch, and P. M. Poggi, "PhaseSpace Geometry and Optimal State Preparation in Quantum Metrology with Collective Spins", PRX QUANTUM 4, 020314 (2023), DOI: 10.1103/PRXQuantum.4.020314
We revisit wellknown protocols in quantum metrology using collective spins and propose a unifying picture for optimal state preparation based on a semiclassical description in phase space. We show how this framework allows for quantitative predictions of the timescales required to prepare various metrologically useful states, and that these predictions remain accurate even for moderate system sizes, surprisingly far from the classical limit. Furthermore, this framework allows us to build a geometric picture that relates optimal (exponentially fast) entangled probe preparation to the existence of separatrices connecting saddle points in phase space. We illustrate our results with the paradigmatic examples of the twoaxis countertwisting and twistingandturning Hamiltonians, where we provide analytical expressions for all the relevant optimal timescales. Finally, we propose a generalization of these models to include pbody collective interaction (or porder twisting), beyond the usual case of p = 2. Using our geometric framework, we prove a nogo theorem for the local optimality of these models for p > 2.

M. H. MuñozArias, K. Chinni, and Pablo M. Poggi (Deutsch group), "Floquet time crystals in driven spin systems with alltoall pbody interactions", PHYSICAL REVIEW RESEARCH 4, 023018 (2022),
DOI: 10.1103/PhysRevResearch.4.023018
We show the emergence of Floquet time crystal (FTC) phases in the Floquet dynamics of periodically driven pspin models, which describe a collection of spin1/2 particles with alltoall pbody interactions. Given the meanfield nature of these models, we treat the problem exactly in the thermodynamic limit and show that, for a given p, these systems can host various robust timecrystalline responses with period nT, where T is the period of the drive and n an integer between 2 and p. In particular, the case of fourbody interactions (p = 4) gives rise to both a usual perioddoubling crystal and also a periodquadrupling phase. We develop a comprehensive framework to predict robust subharmonic response in classical areapreserving maps, and use this as a basis to predict the occurrence and characterize the stability of the resulting meanfield FTC phases in the quantum regime. Our analysis reveals that the robustness of the timecrystal behavior is reduced as their period increases, and establishes a connection between the emergence of time crystals, described by eigenstate ordering and robust subharmonic response, and the phenomenology of excited state and dynamical quantum phase transitions. Finally, for the models hosting two or more coexisting time crystal phases, we define protocols where the periodic subharmonic response of the system can be varied in time via the nonperiodic modulation of an external control parameter.

TH Wu, L. Ledezma, C. Fredrick, P. Sekhar, R. Sekine, Q. Guo, R. M. Briggs, A. Marandi, and S. A. Diddams, "Visible to Ultraviolet Frequency Comb Generation in Lithium Niobate Nanophotonic Waveguides", Nat. Photon. (2024), DOI: 10.1038/s41566023013640
The introduction of nonlinear nanophotonic devices to the field of optical frequency comb metrology has enabled new opportunities for lowpower and chipintegrated clocks, highprecision frequency synthesis, and broad bandwidth spectroscopy. However, most of these advances remain constrained to the nearinfrared region of the spectrum, which has restricted the integration of frequency combs with numerous quantum and atomic systems in the ultraviolet and visible. Here, we overcome this shortcoming with the introduction of multisegment nanophotonic thinfilm lithium niobate (LN) waveguides that combine engineered dispersion and chirped quasiphase matching for efficient supercontinuum generation via the combination of $\chi^{(2)}$ and $\chi^{(3)}$ nonlinearities. With only 90 pJ of pulse energy at 1550 nm, we achieve gapfree frequency comb coverage spanning 330 to 2400 nm. The conversion efficiency from the nearinfrared pump to the UVVisible region of 350550 nm is nearly 20\%. Harmonic generation via the $\chi^{(2)}$ nonlinearity in the same waveguide directly yields the carrierenvelope offset frequency and a means to verify the comb coherence at wavelengths as short as 350 nm. Our results provide an integrated photonics approach to create visible and UV frequency combs that will impact precision spectroscopy, quantum information processing, and optical clock applications in this important spectral window.

H. Liu, G. M. Brodnik, J. Zang, D. R. Carlson, J. A. Black, S. B. Papp, "Threshold and laserconversion in nanostructuredresonator parametric oscillators", Phys. Rev. Lett. 132, 023801 (2024), DOI: 10.1103/PhysRevLett.132.023801
We explore optical parametric oscillation (OPO) in nanophotonic resonators, enabling arbitrary, nonlinear phasematching and nearly lossless control of energy conversion. Such pristine OPO laser converters are determined by nonlinear lightmatter interactions, making them both technologically flexible and broadly reconfigurable. We utilize a nanostructured innerwall modulation in the resonator to achieve universal phasematching for OPOlaser conversion, but coherent backscattering also induces a counterpropagating pump laser. This depletes the intraresonator optical power in either direction, increasing the OPO threshold power and limiting laserconversion efficiency, the ratio of optical power in target signal and idler frequencies to the pump. We develop an analytical model of this system that emphasizes an understanding of optimal laser conversion and threshold behaviors, and we use the model to guide experiments with nanostructuredresonator OPO laserconversion circuits, fully integrated on chip and unlimited by groupvelocity dispersion. Our work demonstrates the fundamental connection between OPO laserconversion efficiency and the resonator coupling rate, subject to the relative phase and power of counterpropagating pump fields. We achieve (40$\pm$4) mW of onchip power, corresponding to (41$\pm$4)\% conversion efficiency, and discover a path toward nearunity OPO laser conversion efficiency.

JR Li, W. G. Tobias, K. Matsuda, C. Miller, G. Valtolina, L. De Marco, R. R. W. Wang, L. Lassablière, G. Quéméner, J. L. Bohn & J. Ye, "Tuning of dipolar interactions and evaporative cooling in a threedimensional molecular quantum gas", Nature Physics 17, 1144–1148 (2021), DOI: 10.1038/s41567021013296
Ultracold polar molecules possess longrange, anisotropic and tunable dipolar interactions, providing opportunities to probe quantum phenomena that are inaccessible with existing cold gas platforms. However, experimental progress has been hindered by the dominance of twobody loss over elastic interactions, which prevents efficient evaporative cooling. Although recent work has demonstrated controlled interactions by confining molecules to a twodimensional geometry, a general approach for tuning molecular interactions in a threedimensional stable system has been lacking. Here we demonstrate tunable elastic dipolar interactions in a bulk gas of ultracold $^{40}K^{87}Rb$ molecules in three dimensions, facilitated by an electric fieldinduced shielding resonance that suppresses the reactive loss by a factor of 30. This improvement in the ratio of elastic to inelastic collisions enables direct thermalization. The thermalization rate depends on the angle between the collisional axis and the dipole orientation controlled by an external electric field, a direct manifestation of the anisotropic dipolar interaction. We achieve evaporative cooling mediated by the dipolar interactions in three dimensions. This work demonstrates full control of a longlived bulk quantum gas system with tunable longrange interactions, paving the way for the study of collective quantum manybody physics.

L. R. Liu, P. B. Changala, M. L. Weichman, Q. Liang, J. Toscano, J. Klos, S. Kotochigova, D. J. Nesbitt, and J. Ye, “Collisioninduced C60 rovibration relaxation probed by stateresolved nonlinear spectroscopy”, Phys. Rev. X Quantum 3, 030332 (2022), DOI: 10.1103/prxquantum.3.030332
Quantum stateresolved spectroscopy was recently achieved for $C_{60}$ molecules when cooled by buffer gas collisions and probed with a midinfrared frequency comb. This rovibrational quantum state resolution for the largest molecule on record is facilitated by the remarkable symmetry and rigidity of $C_{60}$, which also present new opportunities and challenges to explore energy transfer between quantum states in this manyatom system. Here we combine statespecific optical pumping, buffer gas collisions, and ultrasensitive intracavity nonlinear spectroscopy to initiate and probe the rotationvibration energy transfer and relaxation. This approach provides the first detailed characterization of $C_{60}$ collisional energy transfer for a variety of collision partners, and determines the rotational and vibrational inelastic collision cross sections. These results compare well with our theoretical modeling of the collisions, and establish a route towards quantum state control of a new class of unprecedentedly large molecules.

K. Kim, A. Aeppli, T. Bothwell, and J. Ye, “Evaluation of lattice light shift at low 10^{19} uncertainty for a shallow lattice Sr optical clock”, Phys. Rev. Lett. 130, 113203 (2023), DOI: 10.1103/PhysRevLett.130.113203
A WannierStark optical lattice clock has demonstrated unprecedented measurement precision for optical atomic clocks. We present a systematic evaluation of the lattice light shift, a necessary next step for establishing this system as an accurate atomic clock. With precise control of the atomic motional states in the lattice, we report accurate measurements of the multipolar and the hyperpolar contributions and the operational lattice light shift with a fractional frequency uncertainty of $3.5 \times 10^{19}$.

D. GonzálezCuadra, D. Bluvstein, M. Kalinowski, R. Kaubruegger, N. Maskara, P. Naldesi, T. V. Zache, A. M. Kaufman, M. D. Lukin, H. Pichler, B. Vermesch, J. Ye, and P. Zoller, “Fermionic quantum processing with programmable neutral atom arrays”, Proc. National Academy Science (PNAS), in press (2023), DOI: 10.1073/pnas.2304294120
Simulating the properties of manybody fermionic systems is an outstanding computational challenge relevant to material science, quantum chemistry, and particle physics. Although qubitbased quantum computers can potentially tackle this problem more efficiently than classical devices, encoding nonlocal fermionic statistics introduces an overhead in the required resources, limiting their applicability on nearterm architectures. In this work, we present a fermionic quantum processor, where fermionic models are locally encoded in a fermionic register and simulated in a hardwareefficient manner using fermionic gates. We consider in particular fermionic atoms in programmable tweezer arrays and develop different protocols to implement nonlocal tunneling gates, guaranteeing Fermi statistics at the hardware level. We use this gate set, together with Rydbergmediated interaction gates, to find efficient circuit decompositions for digital and variational quantum simulation algorithms, illustrated here for molecular energy estimation. Finally, we consider a combined fermionqubit architecture, where both the motional and internal degrees of freedom of the atoms are harnessed to efficiently implement quantum phase estimation, as well as to simulate lattice gauge theory dynamics.

R. Hutson, W. R. Milner, L. Yan, J. Ye, and C. Sanner, “Observation of mHzlevel cooperative Lamb shifts in an optical atomic clock”, Science 383, 384 – 387 (2024), DOI: 10.1126/science.adh4477
We report on the direct observation of resonant electric dipoledipole interactions in a cubic array of atoms in the manyexcitation limit. The interactions, mediated by singleatom couplings to the shared electromagnetic vacuum, are shown to produce spatiallydependent cooperative Lamb shifts when spectroscopically interrogating the mHzwide optical clock transition in strontium87. We show that the ensembleaveraged shifts can be suppressed below the level of evaluated systematic uncertainties for stateoftheart optical atomic clocks. Additionally, we demonstrate that excitation of the atomic dipoles near a Bragg angle can enhance these effects by nearly an order of magnitude compared to nonresonant geometries. Given the remarkable precision of frequency measurements and the high accuracy of the modeled response, our work demonstrates that such a clock is a novel platform for studies of the quantum manybody physics of spins with longrange interactions mediated by propagating photons.

Q. Liang, Y. Chan, J. Toscano, K. K. Bjorkman, L. A. Leinwand, R. Parker, E. Nozik, D. J. Nesbitt, and J. Ye, “Breath analysis by ultrasensitive broadband laser spectroscopy detects SARSCoV2 infection”, J. Breath Res. 17, 036001 (2023), DOI: 10.1088/17527163/acc6e4
Rapid testing is essential to fighting pandemics such as coronavirus disease 2019 (COVID19), the disease caused by the severe acute respiratory syndrome coronavirus 2 (SARSCoV2). Exhaled human breath contains multiple volatile molecules providing powerful potential for noninvasive diagnosis of diverse medical conditions. We investigated breath detection of SARSCoV2 infection using cavityenhanced direct frequency comb spectroscopy (CEDFCS), a stateoftheart laser spectroscopic technique capable of a realtime massive collection of broadband molecular absorption features at rovibrational quantum state resolution and at partspertrillion volume detection sensitivity. Using a total of 170 individual breath samples (83 positive and 87 negative with SARSCoV2 based on reverse transcription polymerase chain reaction tests), we report excellent discrimination capability for SARSCoV2 infection with an area under the receiveroperatingcharacteristics curve of 0.849(4). Our results support the development of CEDFCS as an alternative, rapid, noninvasive test for COVID19 and highlight its remarkable potential for optical diagnoses of diverse biological conditions and disease states.

L. R. Liu, D. Rosenberg, P. B. Changala, P. J. D. Crowley, D. J. Nesbitt, N. Y. Yao, T. Tscherbul, and J. Ye, “Ergodicity breaking in rapidly rotating C60 fullerene”, Science, 17, Vol 381, Issue 6659, pp. 778783 (2023), DOI: 10.1126/science.adi6354
Ergodicity, the central tenet of statistical mechanics, requires that an isolated system will explore all of its available phase space permitted by energetic and symmetry constraints. Mechanisms for violating ergodicity are of great interest for probing nonequilibrium matter and for protecting quantum coherence in complex systems. For decades, polyatomic molecules have served as an intriguing and challenging platform for probing ergodicity breaking in vibrational energy transport, particularly in the context of controlling chemical reactions. Here, we report the observation of rotational ergodicity breaking in an unprecedentedly large and symmetric molecule, $^{12}C_{60}$. This is facilitated by the first ever observation of icosahedral rovibrational fine structure in any physical system, first predicted for $^{12}C_{60}$ in 1986. The ergodicity breaking exhibits several surprising features: first, there are multiple transitions between ergodic and nonergodic regimes as the total angular momentum is increased, and second, they occur well below the traditional vibrational ergodicity threshold. These peculiar dynamics result from the molecules' unique combination of symmetry, size, and rigidity, highlighting the potential of fullerenes to uncover emergent phenomena in mesoscopic quantum systems.

C. A. Weidner, S. Z. Ahmed, J. H. M. Jensen, J. F. Sherson, and H. J. Lewandowski, "Investigating student use of a flexible tool for simulating and visualizing quantum mechanics", 2020 Physics Education Research Conference Proceedings 563568 (2020), DOI: 10.1119/perc.2020.pr.weidner
As education researchers gain a broader understanding of how students learn quantum mechanics, new pedagogical and technical resources are being developed to facilitate student learning. To further researchbased knowledge of student learning of quantum mechanics, we present a study on the use of Quantum Composer, a flexible, flowbased tool for the exploration and simulation of quantum mechanical systems in one dimension. To explore Composer's impact on students' knowledge of quantum mechanics, we carried out thinkaloud interviews where students worked through an exercise exploring the statics and timedynamics of quantum states in single and double harmonic well potentials. Student Outcomes are then crosscoded with their observed Interactions with Composer. We find that defined Outcomes of Recollection, Reinforcement and Discovery happen most often when students are using the Composer tools that allow them to visualize quantum states, simulate their time dynamics, and change parameters repeatedly in order to understand how systems are represented in both the static and dynamic cases.

C. D. Aiello, D. D. Awschalom, H. Bernien, T. Brower, K. R. Brown, T. A. Brun, J. R. Caram, E. Chitambar, R. Di Felice, K. M. Edmonds, M. F. J .Fox, S. Haas, A. W. Holleitner, E. R. Hudson, J. H. Hunt, R. Joynt, S. Koziol, M. Larsen, H. J. Lewandowski, D. T. McClure, J. Palsberg, G. Passante, K. L. Pudenz, C. J. K. Richardson, J. L. Rosenberg, R. S. Ross, M. Saffman, M. Singh, D. W. Steuerman, C. Stark, J. Thijssen, N. Vamivakas, J. D. Whitfield, B. M. Zwickl, "Achieving a quantum smart workforce", Quantum Science And Technology 6, 030501 (2021), DOI: 10.1088/20589565/abfa64
Interest in building dedicated quantum information science and engineering (QISE) education programs has greatly expanded in recent years. These programs are inherently convergent, complex, often resource intensive and likely require collaboration with a broad variety of stakeholders. In order to address this combination of challenges, we have captured ideas from many members in the community. This manuscript not only addresses policy makers and funding agencies (both public and private and from the regional to the international level) but also contains needs identified by industry leaders and discusses the difficulties inherent in creating an inclusive QISE curriculum. We report on the status of eighteen postsecondary education programs in QISE and provide guidance for building new programs. Lastly, we encourage the development of a comprehensive strategic plan for quantum education and workforce development as a means to make the most of the ongoing substantial investments being made in QISE.

V. Borish, A. Werth, and H. J. Lewandowski, "Seeing quantum mechanics: The role of quantum experiments", 2022 PERC Proceedings (Grand Rapids, MI, July 1314, 2022), edited by B. W. Frank, D. L. Jones, and Q. X. Ryan, DOI: 10.1119/perc.2022.pr.Borish
The second quantum revolution has prompted not only research in quantum science and technology, but also research on how best to educate students who may enter this burgeoning field. Much of the conversation around quantum science education has focused on students' conceptual learning or skills desired by potential employers; there has been an absence of work understanding how laboratory courses and experiments contribute to undergraduate quantum education. To begin understanding the role quantum experiments may play, we surveyed instructors who implement experiments with single and entangled photons in undergraduate lab courses and found that one of the most important learning goals was to "see quantum mechanics in real life.'' To better understand this goal, we interviewed 15 of the surveyed instructors asking what seeing quantum mechanics means to them and why they believe it is an important part of students' education. We present emergent themes from a qualitative coding analysis of these interviews, which begin to elucidate how instructors think about seeing quantum mechanics and what learning goals instructors hope seeing quantum mechanics  and working with quantum experiments more generally  will help students achieve.

V. Borish and H. J. Lewandowski. "Implementation and goals of quantum optics experiments in undergraduate instructional labs", Phys. Rev. Phys. Educ. Res. 19, 010117 (2023), DOI: 10.1103/PhysRevPhysEducRes.19.010117
As quantum information science and technology (QIST) is becoming more prevalent and occurring not only in research labs but also in industry, many educators are considering how best to incorporate learning about quantum mechanics into various levels of education. Although much of the focus has been on quantum concepts in nonlab courses, current work in QIST has a substantial experimental component. Many instructors of undergraduate lab courses want to provide their students the opportunity to work with quantum experiments. One common way this is done is through a sequence of quantum optics experiments often referred to as the “singlephoton experiments.” These experiments demonstrate fundamental quantum phenomena with equipment common to research labs; however, they are resource intensive and cannot be afforded by all institutions. It is therefore imperative to know what unique affordances these experiments provide to students. As a starting point, we surveyed and interviewed instructors who use the singlephoton experiments in undergraduate courses, asking how and why they use the experiments. We describe the most commonly used experiments in both quantum and beyondfirstyear lab courses, the prevalence of actions the students perform, and the learning goals, ranging from conceptual knowledge to lab skills to student affect. Finally, we present some strategies from these data demonstrating how instructors have addressed the common challenges of preparing students to work with conceptually and technically complex experiments and balancing the practice of technical skills with the completion of the experiments.

H. Zhang, A. Chu, C. Luo, J. K. Thompson, A. M. Rey, "Control and amplification of Bloch oscillations via photonmediated interactions", Phys. Rev. Research 2023, 5 (3), L032039, DOI: 10.1103/PhysRevResearch.5.L032039
We propose a scheme to control and enhance atomic Bloch oscillations via photonmediated interactions in an optical lattice supported by a standingwave cavity with incommensurate lattice and cavity wavelengths. Our scheme uses positiondependent atomlight couplings to spatially prepare, from a thermal gas, to an array of atoms at specific lattice sites. On this initial state we take advantage of dispersive positiondependent atomcavity couplings to perform nondestructive measurements of singleparticle Bloch oscillations, and to generate longrange interactions selftuned by atomic motion. The latter leads to the generation of dynamical phase transitions in the deep lattice regime and the amplification of Bloch oscillations in the shallow lattice regime. Our work introduces new possibilities accessible in stateoftheart cavity QED experiments for the exploration of manybody dynamics in selftunable potentials.

D. Barberena, R. J. LewisSwan, A. M. Rey, and J. K. Thompson, "Ultra Narrow Linewidth Frequency Reference via Measurement and Feedback", C. R. Phys. 2023, 24 (S3), 1–14, DOI: 10.5802/crphys.146
The generation of very narrow linewidth light sources is of great importance in modern science. One such source is the superradiant laser, which relies on collectively interacting ultra long lived dipoles driven by incoherent light. Here we discuss a different way of generating spectrally pure light by coherently driving such dipoles inside an optical QED cavity. The light exiting the cavity carries information about the detuning between the driving light and the atomic transition, but is also affected by the noise originating from all the decoherence processes that act on the combined atomcavity system. We calculate these effects to obtain fundamental limits for frequency estimation and stabilization across a range of values of input light intensities and atomlight interaction strengths, estimate these limits in stateoftheart cavity experiments with alkalineearth atoms and identify favorable operating conditions. We find that the achievable linewidths are comparable to those of the superradiant laser.

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D. J. Young, A. Chu, E. Y. Song, D. Barberena, D. Wellnitz, Z. Niu, V. M. Schäfer, R. J. LewisSwan, A. M. Rey, and J. K. Thompson, "Observing Dynamical Phases of BCS Superconductors in a Cavity QED Simulator", Nature 2024, 625 (7996), 679–684 DOI: 10.1038/s4158602306911x
In conventional BardeenCooperSchrieffer (BCS) superconductors, electrons with opposite momenta bind into Cooper pairs due to an attractive interaction mediated by phonons in the material. While superconductivity naturally emerges at thermal equilibrium, it can also emerge out of equilibrium when the system's parameters are abruptly changed. The resulting outofequilibrium phases are predicted to occur in real materials and ultracold fermionic atoms but have not yet been directly observed. This work realizes an alternate way to generate the proposed dynamical phases using cavity quantum electrodynamics (cavity QED). Our system encodes the presence or absence of a Cooper pair in a longlived electronic transition in $^{88}Sr$ atoms coupled to an optical cavity and represents interactions between electrons as photonmediated interactions through the cavity. To fully explore the phase diagram, we manipulate the ratio between the singleparticle dispersion and the interactions after a quench and perform realtime tracking of subsequent dynamics of the superconducting order parameter using nondestructive measurements. We observe regimes where the order parameter decays to zero ("phase I"), assumes a nonequilibrium steadystate value ("phase II"), or exhibits persistent oscillations ("phase III") in the form of a selfgenerated Floquet phase. The capability to emulate these dynamical phases in optical cavities without real Cooper pairs demonstrates that programmable simulators can overcome many challenges faced by traditional approaches. This opens up exciting prospects for quantum simulation, including the potential to engineer unconventional superconductors and to probe beyond meanfield effects like the spectral form factor, and for increasing coherence time for quantum sensing.

M. Mamaev, T. Bilitewski, B. Sundar, and A. M. Rey, "Resonant Dynamics of Strongly Interacting SU(n) Fermionic Atoms in a Synthetic Flux Ladder", PRX Quantum 3, 030328 (2022), DOI: 10.1103/PRXQuantum.3.030328
We theoretically study the dynamics of nlevel spinorbit coupled alkalineearth fermionic atoms with SU(n) symmetric interactions. We consider threedimensional lattices with tunneling along one dimension, and the internal levels treated as a synthetic dimension, realizing an nleg flux ladder. Laser driving is used to couple the internal levels and to induce an effective magnetic flux through the ladder. We focus on the dense and strongly interacting regime, where in the absence of flux the system behaves as a Mott insulator with suppressed motional dynamics. At integer and fractional ratios of the laser Rabi frequency to the onsite interactions, the system exhibits resonant features in the dynamics. These resonances occur when interactions help overcome kinetic constraints upon the tunneling of atoms, thus enabling motion. Different resonances allow for the development of complex chiral current patterns. The resonances resemble those appearing in the longitudinal Hall resistance when the magnetic field is varied. We characterize the dynamics by studying the system’s longtime relaxation behavior as a function of flux, number of internal levels n, and interaction strength. We observe a series of nontrivial prethermal plateaus caused by the emergence of resonant processes at successive orders in perturbation theory. We discuss protocols to observe the predicted phenomena under current experimental conditions.

A. Shankar, E. A. Yuzbashyan, V. Gurarie, P. Zoller, J. J. Bollinger, and A. M. Rey, "Simulating Dynamical Phases of Chiral p+ip Superconductors with a Trapped ion Magnet", PRX Quantum 3, 040324 (2022), DOI: 10.1103/PRXQuantum.3.040324
Twodimensional p+ip superconductors and superfluids are systems that feature chiral behavior emerging from the Cooper pairing of electrons or neutral fermionic atoms with nonzero angular momentum. Their realization has been a longstanding goal because they offer great potential utility for quantum computation and memory. However, they have so far eluded experimental observation both in solidstate systems as well as in ultracold quantum gases. Here, we propose to leverage the tremendous control offered by rotating twodimensional trappedion crystals in a Penning trap to simulate the dynamical phases of twodimensional p+ip superfluids. This is accomplished by mapping the presence or absence of a Cooper pair into an effective spin1/2 system encoded in the ions’ electronic levels. We show how to infer the topological properties of the dynamical phases, and discuss the role of beyond meanfield corrections. More broadly, our work opens the door to use trappedion systems to explore exotic models of topological superconductivity and also paves the way to generate and manipulate skyrmionic spin textures in these platforms.

J. T. Young, S. R. Muleady, M. A. Perlin, A. M. Kaufman, and A. M. Rey, "Enhancing spin squeezing using softcore interactions", Phys. Rev. Research 5, L012033 (2023), DOI: 10.1103/PhysRevResearch.5.L012033
We propose a protocol for preparing spin squeezed states in controllable atomic, molecular, and optical systems, with particular relevance to emerging optical clock platforms compatible with Rydberg interactions. By combining a shortrange, softcore potential with an external drive, we can transform naturally emerging Ising interactions into an XX spin model while opening a manybody gap. The gap helps maintain the system within a collective manifold of states where metrologically useful spin squeezing can be generated. We examine the robustness of our protocol to experimentally relevant decoherence and show favorable performance over typical protocols lacking gap protection. For example, in a 14×14 system, we observe that softcore interactions can generate spin squeezing comparable to an alltoall Ising model even in the presence of relevant decoherence, the same amount of squeezing as the decoherencefree XX spin model with $1/{r^{3}}$ dipolar interactions, and a 5.8 dB gain over the decoherencefree XX spin model with $1/{r^{6}}$ interactions.

T. Bilitewski, G. DomínguezCastro, D. Wellnitz, A. M. Rey, and L. Santos, "Momentumselective pair creation of spin excitations in dipolar bilayers", arXiv:2302.09059 Submitted (2023), DOI: 10.48550/arXiv.2302.09059
We study the temporal growth and spatial propagation of quantum correlations in a twodimensional bilayer realising a spin1/2 quantum XXZ model with couplings mediated by longrange and anisotropic dipolar interactions. Starting with an initial state consisting of spins with opposite magnetization in each of the layers, we predict the emergence of a momentumdependent dynamic instability in the spin structure factor that results, at short times, in the creation of pairs of excitations at exponentially fast rates. The created pairs present a characteristic momentum distribution that can be tuned by controlling the dipolar orientation, the layer separation or the dipolar couplings. The predicted behavior remains observable at very low filling fractions, making it accessible in stateoftheart experiments with Rydberg atoms, magnetic atoms, and polar molecule arrays.

B. Sundar, D. Barberena, A. M. Rey, and A. Orioli, "Squeezing multilevel atoms in dark states via cavity superradiance", Phys. Rev. Lett. 132, 033601 (2024), DOI: 10.1103/PhysRevLett.132.033601
We describe a method to create and store scalable and longlived entangled spinsqueezed states within a manifold of manybody cavity dark states using collective emission of light from multilevel atoms inside an optical cavity. We show that the system can be tuned to generate squeezing in a dark state where it will be immune to superradiance. We also show more generically that squeezing can be generated using a combination of superradiance and coherent driving in a bright state, and subsequently be transferred via singleparticle rotations to a dark state where squeezing can be stored. Our findings, readily testable in current optical cavity experiments with alkalineearthlike atoms, can open a path for dissipative generation and storage of metrologically useful states in optical transitions.

J. Franke, S. R. Muleady, R. Kaubruegger, F. Kranzl, R. Blatt, A. M. Rey, M. Joshi, and C. Roos, "Quantumenhanced sensing on an optical transition via emergent collective quantum correlations", arXiv:2303.10688 Submitted (2023), DOI: 10.48550/arXiv.2303.10688
The control over quantum states in atomic systems has led to the most precise optical atomic clocks to date. Their sensitivity is currently bounded by the standard quantum limit, a fundamental floor set by quantum mechanics for uncorrelated particles, which can nevertheless be overcome when operated with entangled particles. Yet demonstrating a quantum advantage in real world sensors is extremely challenging and remains to be achieved aside from two remarkable examples, LIGO and more recently HAYSTAC. Here we illustrate a pathway for harnessing scalable entanglement in an optical transition using 1D chains of up to 51 ions with statedependent interactions that decay as a powerlaw function of the ion separation. We show our sensor can be made to behave as a oneaxistwisting (OAT) model, an iconic fully connected model known to generate scalable squeezing. The collective nature of the state manifests itself in the preservation of the total transverse magnetization, the reduced growth of finite momentum spinwave excitations, the generation of spin squeezing comparable to OAT (a Wineland parameter of $3.9\pm0.3$ dB for only N = 12 ions) and the development of nonGaussian states in the form of atomic multiheaded cat states in the Qdistribution. The simplicity of our protocol enables scalability to large arrays with minimal overhead, opening the door to advances in timekeeping as well as new methods for preserving coherence in quantum simulation and computation. We demonstrate this in a Ramseytype interferometer, where we reduce the measurement uncertainty by $3.2\pm0.5$ dB below the standard quantum limit for N = 51 ions.

S. R. Muleady, M. Yang, S. R. White, and A. M. Rey, "Validating phasespace methods with tensor networks in twodimensional spin models with powerlaw interactions", arXiv:2305.17242 Submitted (2023), DOI: 10.48550/arXiv.2305.17242
Using a recently developed extension of the timedependent variational principle for matrix product states, we evaluate the dynamics of 2D powerlaw interacting XXZ models, implementable in a variety of stateoftheart experimental platforms. We compute the spin squeezing as a measure of correlations in the system, and compare to semiclassical phasespace calculations utilizing the discrete truncated Wigner approximation (DTWA). We find the latter efficiently and accurately captures the scaling of entanglement with system size in these systems, despite the comparatively resourceintensive tensor network representation of the dynamics. We also compare the steadystate behavior of DTWA to thermal ensemble calculations with tensor networks. Our results open a way to benchmark dynamical calculations for twodimensional quantum systems, and allow us to rigorously validate recent predictions for the generation of scalable entangled resources for metrology in these systems.

M. Mamaev, D. Barberena, and A. M. Rey, "Spin squeezing in mixeddimensional anisotropic lattice models", arXiv:2306.05313 Submitted (2023), DOI: 10.48550/arXiv.2306.05313
We describe a theoretical scheme for generating scalable spin squeezing with nearestneighbour interactions between spin1/2 particles in a 3D lattice, which are naturally present in stateoftheart 3D optical lattice clocks. We propose to use strong isotropic Heisenberg interactions within individual planes of the lattice, forcing the constituent spin1/2s to behave as large collective spins. These large spins are then coupled with XXZ anisotropic interactions along a third direction of the lattice. This system can be realized via superexchange interactions in a 3D optical lattice subject to an external linear potential, such as gravity, and in the presence of spinorbit coupling (SOC) to generate spin anisotropic interactions. We show there is a wide range of parameters in this setting where the spin squeezing improves with increasing system size even in the presence of holes.

A. Hattori, S. Corsetti, T. Sneh, M. Notaros, R. Swint, P.T. Callahan, C.D. Bruzewicz, F. Knollmann, R. McConnell, J. Chiaverini, and J. Notaros, “IntegratedPhotonicsBased Architectures for PolarizationGradient and EIT Cooling of Trapped Ions”, Frontiers in Optics (FiO) 2022, paper FM4B.3 (2022), DOI: 10.1364/FIO.2022.FM4B.3
We develop a framework for two advanced trappedion cooling schemes, polarizationgradient and electromagneticallyinducedtransparency cooling, for $^{88}Sr^{+}$ ions using a visiblewavelength integratedphotonics platform and present the design of the key integrated devices.

T. Sneh, A. Hattori, M. Notaros, S. Corsetti, and J. Notaros (Chiaverini group), “Design of Integrated VisibleLight Polarization Rotators and Splitters”, Frontiers in Optics (FiO) 2022, paper JTu5A.48 (2022) DOI: 10.1364/FIO.2022.JTu5A.48
Integrated polarization rotators and splitters are designed for the first time at visible wavelengths. Specifically, an adiabatic polarization rotator, an offaxis polarization rotator, and a modecoupling polarization splitter are designed in a siliconnitride platform.

B. L. Augenbraun, L. Anderegg, C. Hallas, Z. D. Lasner, N. B. Vilas, and J. M. Doyle, "Direct laser cooling of polyatomic molecules", Advances in Atomic, Molecular, and Optical Physics, vol. 72, Ch. 2 (2023), DOI: 10.1016/bs.aamop.2023.04.005
Over the past decade, tremendous progress has been made to extend the tools of laser cooling and trapping to molecules. Those same tools have recently been applied to polyatomic molecules (molecules containing three or more atoms). In this review, we discuss the scientific drive to bring larger molecules to ultralow temperatures, the features of molecular structure that provide the most promising molecules for this pursuit, and some technical aspects of how lasers can be used to control the motion and quantum states of polyatomic molecules. We also present opportunities for and challenges to the use of polyatomic molecules for science and technology.

N. Schine, A. W. Young, W. J. Eckner, M. J. Martin & A. M. Kaufman, "Longlived Bell states in an array of optical clock qubits", Nat. Phys. 18, 1067–1073 (2022), DOI: 10.1038/s4156702201678w
The generation of longlived entanglement in optical atomic clocks is one of the main goals of quantum metrology. Arrays of neutral atoms, where Rydbergbased interactions may generate entanglement between individually controlled and resolved atoms, constitute a promising quantum platform to achieve this. Here we leverage the programmable state preparation afforded by optical tweezers and the efficient strong confinement of a threedimensional optical lattice to prepare an ensemble of strontiumatom pairs in their motional ground state. We engineer global singlequbit gates on the optical clock transition and twoqubit entangling gates via adiabatic Rydberg dressing, enabling the generation of Bell states with a statepreparationandmeasurementcorrected fidelity of 92.8(2.0)\% (87.1(1.6)\% without statepreparationandmeasurement correction). For use in quantum metrology, it is furthermore critical that the resulting entanglement be long lived; we find that the coherence of the Bell state has a lifetime of 4.2(6) s via parity correlations and simultaneous comparisons between entangled and unentangled ensembles. Such longlived Bell states can be useful for enhancing metrological stability and bandwidth. In the future, atomic rearrangement will enable the implementation of manyqubit gates and cluster state generation, as well as explorations of the transverse field Ising model.

S. Omanakuttan, A. Mitra, M. J. Martin, I. H. Deutsch, “Qudit entanglers using quantum optimal control”, PRX Quantum 4, 040333 (2023), DOI: 10.1103/PRXQuantum.4.040333
We study the generation of twoqudit entangling quantum logic gates using two techniques in quantum optimal control. We take advantage of both continuous, Liealgebraic control and digital, Liegroup control. In both cases, the key is access to a timedependent Hamiltonian which can generate an arbitrary unitary matrix in the group SU($d^{2}$). We find efficient protocols for creating highfidelity entangling gates. As a test of our theory, we study the case of qudits robustly encoded in nuclear spins of alkaline earth atoms and manipulated with magnetic and optical fields, with entangling interactions arising from the wellknown Rydberg blockade. We applied this in a case study based on a d=10 dimensional qudit encoded in the I=9/2 nuclear spin in $^{87}Sr$, controlled through a combination of nuclear spinresonance, a tensor ACStark shift, and Rydberg dressing, which allows us to generate an arbitrary symmetric entangling twoqudit gate such as CPhase. Our techniques can be used to implement qudit entangling gates for any $2 \le d \le 10$ encoded in the nuclear spin. We also studied how decoherence due to the finite lifetime of the Rydberg states affects the creation of the CPhase gate and found, through numerical optimization, a fidelity of 0.9985, 0.9980, 0.9942, and 0.9800 for d=2, d=3, d=5, and d=7 respectively. This provides a powerful platform to explore the various applications of quantum information processing of qudits including metrological enhancement with qudits, quantum simulation, universal quantum computation, and quantum error correction.

M. Nie, Y. Xie, B. Li, and S.W. Huang, "Photonic frequency microcombs based on dissipative Kerr and quadratic cavity solitons", Prog. Quant. Electron. 86, 100437 (2022), DOI: 10.1016/j.pquantelec.2022.100437
Optical frequency comb, with precisely controlled spectral lines spanning a broad range, has been the key enabling technology for many scientific breakthroughs. In addition to the traditional implementation based on modelocked lasers, photonic frequency microcombs based on dissipative Kerr and quadratic cavity solitons in highQ microresonators have become invaluable in applications requiring compact footprint, low cost, good energy efficiency, large comb spacing, and access to nonconventional spectral regions. In this review, we comprehensively examine the recent progress of photonic frequency microcombs and discuss how various phenomena can be utilized to enhance the microcomb performances that benefit a plethora of applications including optical atomic clockwork, optical frequency synthesizer, precision spectroscopy, astrospectrograph calibration, biomedical imaging, optical communications, coherent ranging, and quantum information science.

M. Nie, K. Jia, Y. Xie, S. Zhu, Z. Xie, and S.W. Huang, "Synthesized spatiotemporal modelocking and photonic flywheel in multimode mesoresonators", Nature Commun. 13, 6395 (2022), DOI: 10.1038/s41467022341030
Dissipative Kerr soliton (DKS) frequency combs—also known as microcombs—have arguably created a new field in cavity nonlinear photonics, with a strong crossfertilization between theoretical, experimental, and technological research. Spatiotemporal modelocking (STML) not only adds new degrees of freedom to ultrafast laser technology, but also provides new insights for implementing analogue computers and heuristic optimizers with photonics. Here, we combine the principles of DKS and STML to demonstrate the STML DKS by developing an unexplored ultrahighqualityfactor Fabry–Pérot (FP) mesoresonator based on graded index multimode fiber (GRINMMF). Complementing the twostep pumping scheme with a cavity stress tuning method, we can selectively excite either the eigenmode DKS or the STML DKS. Furthermore, we demonstrate an ultralow noise microcomb that enhances the photonic flywheel performance in both the fundamental comb linewidth and DKS timing jitter. The demonstrated fundamental comb linewidth of 400 mHz and DKS timing jitter of 500 attosecond (averaging times up to 25 μs) represent improvements of 25x and 2.5x, respectively, from the stateoftheart. Our results show the potential of GRINMMF FP mesoresonators as an ideal testbed for highdimensional nonlinear cavity dynamics and photonic flywheel with ultrahigh coherence and ultralow timing jitter.

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M. H. Zaheer, N. J. Matjelo, D. B. Hume, M. S. Safronova, D. R. Leibrandt, “Quantum metrology algorithms for dark matter searches with clocks”, arXiv:2302.12956, DOI: 10.48550/arXiv.2302.12956
Quantum algorithms such as dynamical decoupling can be used to improve the sensitivity of a quantum sensor to a signal while suppressing sensitivity to noise. Atomic clocks are among the most sensitive quantum sensors, with recent improvements in clock technology allowing for unprecedented precision and accuracy. These clocks are highly sensitive to variations in fundamental constants, making them ideal probes for local ultralight scalar dark matter. Further improvements to the sensitivity is expected in proposed nuclear clocks based on the thorium 229m isomer. We investigate the use of various quantum metrology algorithms in the search for dark matter using quantum clocks. We propose a new broadband dynamical decoupling algorithm and compare it with quantum metrology protocols that have been previously proposed and demonstrated, namely differential spectroscopy and narrowband dynamical decoupling. We conduct numerical simulations of scalar dark matter searches with realistic noise sources and accounting for dark matter decoherence. Finally, we discuss an alternative thorium nuclear transition excitation method that bypasses the technical challenges associated with vacuum ultraviolet lasers.

K. Cui, J. Valencia, K. T. Boyce, E. R. Clements, D. R. Leibrandt, and D. B. Hume, “Scalable Quantum Logic Spectroscopy”, Phys. Rev. Lett. 129, 193603 (2022), DOI: 10.1103/PhysRevLett.129.193603
In quantum logic spectroscopy (QLS), one species of trapped ion is used as a sensor to detect the state of an otherwise inaccessible ion species. This extends precision measurements to a broader class of atomic and molecular systems for applications like atomic clocks and tests of fundamental physics. Here, we develop a new technique based on a Schrödinger cat interferometer to address the problem of scaling QLS to larger ion numbers. We demonstrate the basic features of this method using various combinations of $^{25}Mg^{+}$ logic ions and $^{27}Al^{+}$ spectroscopy ions. We observe higher detection efficiency by increasing the number of $^{25}Mg^{+}$ ions. Applied to multiple $^{27}Al^{+}$, this method will improve the stability of highaccuracy optical clocks and could enable Heisenberglimited QLS.

A. Young, W. Eckner, N. Schine, A. M. Childs, A. Kaufman, "Tweezerprogrammable quantum walks in a Hubbardregime lattice", Science 377, 6608 pp 885889 (2023), DOI: 10.1126/science.abo0608
Quantum walks provide a framework for designing quantum algorithms that is both intuitive and universal. To leverage the computational power of these walks, it is important to be able to programmably modify the graph a walker traverses while maintaining coherence. We do this by combining the fast, programmable control provided by optical tweezers with the scalable, homogeneous environment of an optical lattice. With these tools we study continuoustime quantum walks of single atoms on a square lattice and perform proofofprinciple demonstrations of spatial search with these walks. When scaled to more particles, the capabilities demonstrated can be extended to study a variety of problems in quantum information science, including performing more effective versions of spatial search using a larger graph with increased connectivity.

J.Y. Lee, J. Ramette, M.A. Metlitski, V. Vuletić, W.W. Ho, and S. Choi, "LandauForbidden Quantum Criticality in Rydberg Quantum Simulators", submitted to Phys. Rev. Lett., Phys. Rev. Lett. 131, 083601 (2023), DOI: 10.1103/PhysRevLett.131.083601
The LandauGinzburgWilson theory of phase transitions precludes a continuous transition between two phases that spontaneously break distinct symmetries. However, quantum mechanical effects can intertwine the symmetries, giving rise to an exotic phenomenon called deconfined quantum criticality (DQC). In this work, we study the ground state phase diagram of a onedimensional array of individually trapped neutral atoms interacting strongly via Rydberg states, and demonstrate through extensive numerical simulations that it hosts a variety of symmetrybreaking phases and their transitions including DQC. We show how an enlarged, emergent continuous symmetry arises at the DQCs, which can be experimentally observed in the joint distribution of two distinct order parameters, obtained within measurement snapshots in the standard computational basis. Our findings highlight quantum simulators of Rydberg atoms not only as promising platforms to experimentally realize such exotic phenomena, but also as unique ones allowing access to physical properties not obtainable in traditional experiments.

Y.T. Chen, M. Szurak, Y.C. Yeh, B. Hu, J. de Hond, B. Braverman, and V. Vuletić, "High finesse bowtie cavity for strong atomphoton coupling in Rydberg arrays", Opt. Express 30(21), 3742637435 (2022), 10.1364/OE.469644
We report a highfinesse bowtie cavity designed for atomic physics experiments with Rydberg atom arrays. The cavity has a finesse of 51,000 and a waist of 7.1 μm at the cesium D2 line (852 nm). With these parameters, the cavity is expected to induce strong coupling between a single atom and a single photon, corresponding to a cooperativity per traveling mode of 35 at the cavity waist. To trap and image atoms, the cavity setup utilizes two invacuum aspheric lenses with a numerical aperture (NA) of 0.35 and is capable of housing NA = 0.5 microscope objectives. In addition, the large atommirror distance (≳ 1.5 cm) provides good optical access and minimizes stray electric fields at the position of the atoms. This cavity setup can operate in tandem with a Rydberg array platform, creating a fully connected system for quantum simulation and computation.

P.L. Ocola, I. Dimitrova, B. Grinkemeyer, E. GuardadoSanchez, T. Djordjević, P. Samutpraphoot, V. Vuletić, and M.D. Lukin, "Control and Entanglement of RydbergAtom Qubits Near a Nanoscale Device", Phys. Rev. Lett. 132, 113601 (2024), DOI: 10.1103/PhysRevLett.132.113601
Rydberg atom arrays constitute a promising quantum information platform, where control over several hundred qubits has been demonstrated. Further scaling could significantly benefit from coupling to integrated optical or electronic devices, enabling quantum networking and new control tools, but this integration is challenging due to Rydberg sensitivity to the electric field noise from surfaces. We demonstrate that Rydberg coherence and twoatom entanglement can be generated and maintained at distances of 100 microns from a nanoscale dielectric device. Using coherent manipulation of individual qubits and entanglementassisted sensing, we map the spatiotemporal properties of the electric field environment, enabling its control and the integration of Rydberg arrays with micro and nanoscale devices.

S. Colombo, E. PedrozoPenafiel, and V. Vuletić, "EntanglementEnhanced Optical Atomic Clocks", Appl. Phys. Lett. 121, 210502 (2022), DOI: 10.1063/5.0121372
Recent developments in atomic physics have enabled the experimental generation of manybody entangled states to boost the performance of quantum sensors beyond the Standard Quantum Limit (SQL). This limit is imposed by the inherent projection noise of a quantum measurement. In this Perspective article, we describe the commonly used experimental methods to create manybody entangled states to operate quantum sensors beyond the SQL. In particular, we focus on the potential of applying quantum entanglement to stateoftheart optical atomic clocks. In addition, we present recently developed timereversal protocols that make use of complex states with high quantum Fisher information without requiring subSQL measurement resolution. We discuss the prospects for reaching nearHeisenberg limited quantum metrology based on such protocols.

Z. Vendeiro, J. Ramette, A. Rudelis, M. Chong, J. Sinclair, L. Stewart, A. Urvoy, and V. Vuletić, "Machinelearningaccelerated BoseEinstein condensation", Phys. Rev. Res. 4, 043216 (2022), DOI: 10.1103/PhysRevResearch.4.043216
Machine learning is emerging as a technology that can enhance physics experiment execution and data analysis. Here, we apply machine learning to accelerate the production of a BoseEinstein condensate (BEC) of $^{87}Rb$ atoms by Bayesian optimization of up to 55 control parameters. This approach enables us to prepare BECs of $2.8 \times 10^{3}$ optically trapped 87Rb atoms from a roomtemperature gas in 575 ms. The algorithm achieves the fast BEC preparation by applying highly efficient Raman cooling to near quantum degeneracy, followed by a brief final evaporation. We anticipate that many other physics experiments with complex nonlinear system dynamics can be significantly enhanced by a similar machinelearning approach.

J. Ramette, J. Sinclair, N.P. Breuckmann, and V. Vuletić, "FaultTolerant Connection of Error Corrected Qubits with Noisy Links", submitted to Phys. Rev. Lett.; arXiv:2302.01296, DOI: 10.48550/arXiv.2302.01296
One of the most promising routes towards scalable quantum computing is a modular approach. We show that distinct surface code patches can be connected in a faulttolerant manner even in the presence of substantial noise along their connecting interface. We quantify analytically and numerically the combined effect of errors across the interface and bulk. We show that the system can tolerate 14 times higher noise at the interface compared to the bulk, with only a small effect on the code's threshold and subthreshold behavior, reaching threshold with ∼1% bulk errors and ∼10% interface errors. This implies that faulttolerant scaling of errorcorrected modular devices is within reach using existing technology.

S.C. Carrasco, M.H. Goerz, S.A. Malinovskaya, V. Vuletić, W. Schleich, V.S. Malinovsky, "Dicke State Generation and Extreme Spin Squeezing via Rapid Adiabatic Passage.", Phys. Rev. Lett. 132, 153603 (2024), DOI: 10.1103/PhysRevLett.132.153603
Considering the unique energy level structure of the oneaxis twisting Hamiltonian in combination with standard rotations, we propose the implementation of a rapid adiabatic passage scheme on the Dicke state basis. The method permits to drive Dicke states of the manyatom system into entangled states with maximum quantum Fisher information. The designed states allow to overcome the classical limit of phase sensitivity in quantum metrology and sensing. We show how to generate superpositions of Dicke states, which maximize metrological gain for a Ramsey interferometric measurement. The proposed scheme is remarkably robust to variations of the driving field and the number of atoms.

Z. Li, S. Colombo, C. Shu, G. Velez, S. Pilatowsky Cameo, R. Schmied, S. Choi, M.D. Lukin, E. PedrozoPeñafiel, and V. Vuletić, "Improving Metrology with Quantum Scrambling", Science Vol 380, Issue 6652 pp. 13811384, DOI: 10.1126/science.adg9500
Quantum scrambling describes the spreading of information into many degrees of freedom in quantum systems, such that the information is no longer accessible locally but becomes distributed throughout the system. This idea can explain how quantum systems become classical and acquire a finite temperature, or how in black holes the information about the matter falling in is seemingly erased. We probe the exponential scrambling of a multiparticle system near a bistable point in phase space and utilize it for entanglementenhanced metrology. A timereversal protocol is used to observe a simultaneous exponential growth of both the metrological gain and the outoftimeorder correlator, thereby experimentally verifying the relation between quantum metrology and quantum information scrambling. Our results show that rapid scrambling dynamics capable of exponentially fast entanglement generation are useful for practical metrology, resulting in a 6.8(4)decibel gain beyond the standard quantum limit.

T. Na Narong, T. Liu, N. Raghuram, and L Hollberg, “Stimulated slowing of Yb atoms on the narrow 1S0 → 3P1 transition”, Phys. Rev. A 104, 053117 (2021), DOI: 10.1103/PhysRevA.104.053117
We analyzed bichromatic and polychromatic stimulated forces for laser cooling and trapping of Yb atoms using only the narrow $^{1}S_{0} \rightarrow ^{3}P_{1}$ transition. Our model is based on numerical solutions of optical Bloch equations for twolevel atoms driven by multiple timedependent fields combined with Monte Carlo simulations, which account for realistic experimental conditions such as atomic beam divergence, geometry, and Gaussian laser modes. Using 1 W of laser power, we predict a loading rate of ≈ 108 atoms/s into a 556nm magnetooptical trap (MOT) with a slowing force of ≈ $60F_{rad}$. We show that a squarewave modulation can produce similar stimulated forces with almost twice the velocity range and improve the MOT loading rate of Yb atoms by up to 70%.

V. Schkolnik, D. Budker, O. Fartmann, V. Flambaum, L. Hollberg, T. Kalaydzhyan, S. Kolkowitz, M. Krutzik, A. Ludlow, N. Newbury, C. Pyrlik, L. Sinclair, Y. Stadnik, I. Tietje, J. Ye, and J. Williams, “Optical Atomic Clock aboard an Earthorbiting Space Station (OACESS): Enhancing searches for physics beyond the standard model in space,” Quantum Science and Technology, Volume 8, Number 1, Focus on Cold Atoms in Space, Vladimir Schkolnik et al 2023 Quantum Sci. Technol. 8 014003, DOI: 10.1088/20589565/ac9f2b
We present a concept for a highprecision optical atomic clock (OAC) operating on an Earthorbiting space station. This pathfinder science mission will compare the spacebased OAC with one or more ultrastable terrestrial OACs to search for spacetimedependent signatures of dark scalar fields that manifest as anomalies in the relative frequencies of stationbased and groundbased clocks. This opens the possibility of probing models of new physics that are inaccessible to purely groundbased OAC experiments where a dark scalar field may potentially be strongly screened near Earth's surface. This unique enhancement of sensitivity to potential dark matter candidates harnesses the potential of spacebased OACs.

G. Spektor, D. Carlson, Z. Newman, J. L. Skarda, N. Sapra, L. Su, S. Jammi, A. R. Ferdinand, A. Agrawal, J. Vučković, and S. B. Papp, "Universal visible emitters in nanoscale integrated photonics", Optica Vol. 10, Issue 7, pp. 871879 (2023), DOI: 10.1364/OPTICA.486747
Visible wavelengths of light control the quantum matter of atoms and molecules and are foundational for quantum technologies, including computers, sensors, and clocks. The development of visible integrated photonics opens the possibility for scalable circuits with complex functionalities, advancing both the scientific and technological frontiers. We experimentally demonstrate an inverse design approach based on superposition of guidedmode sources, allowing the generation and full control of freespace radiation directly from within a single 150 nm layer Ta2O5, showing low loss across visible and nearinfrared spectra. We generate diverging circularlypolarized beams at the challenging 461 nm wavelength that can be directly used for magnetooptical traps of strontium atoms, constituting a fundamental building block for a range of atomicphysicsbased quantum technologies. Our generated topological vortex beams and spatiallyvarying polarization emitters could open unexplored lightmatter interaction pathways, enabling a broad new photonicatomic paradigm. Our platform highlights the generalizability of nanoscale devices for visiblelaser emission and will be critical for scaling quantum technologies.

J. A. Black, Z. L. Newman, S.P. Yu, D. R. Carlson, and S. B. Papp, "Nonlinear Networks for Arbitrary Optical Synthesis", Phys. Rev. X 13, 021027 (2023), DOI: 10.1103/PhysRevX.13.021027
Nonlinear wavelength conversion is a powerful control of light, especially when implemented at the nanoscale with integrated photonics. However, strict energy conservation and phasematching require ments constrain the converted output. To overcome these constraints and enable novel functionalities, we introduce nonlinear networks—systems of nonlinear photonic elements that observe a programmable set of conservation rules. We highlight the diverse capabilities of nonlinear networks by demonstrating an optical frequency synthesizer, which operates at nearly arbitrary output frequency exceeding the state of the art in synthesized conversion bandwidth. Using a codesigned microresonator network, our synthesizer is based on fourwave mixing (FWM) spectral translation of a tunable laser and a frequency comb. Energy conservation in FWM provides deterministic synthesis, and it allows a nearly arbitrary frequency tuning range by the dependence of resonant FWM on groupvelocity dispersion, temperature, and input laser frequency. Moreover, we take advantage of efficient parametric amplification intrinsic to nonlinear networks. We operate spectral translation across output ranges up to 200 THz, and we characterize the synthesizer through precise metrology, demonstrating < 0.1 Hz absolute accuracy. Our experiments introduce nonlinear networks that perform complex functionalities, including optical synthesis with nearly limitless bandwidth.

C. Ropp, W. Zhu, A. Yulaev, D. Westly, G. Simelgor, A. Rakholia, W. Lunden, D. Sheredy, M. M. Boyd, S. Papp, A. Agrawal, and V. Aksyuk, "Integrating planar photonics for multibeam generation and atomic clock packaging on chip", Light Sci. Appl. 12, 83 (2023), DOI: 10.1038/s4137702301081x
The commercialization of atomic technologies requires replacing laboratoryscale laser setups with compact and manufacturable optical platforms. Complex arrangements of freespace beams can be generated on chip through a combination of integrated photonics and metasurface optics. In this work, we combine these two technologies using flipchip bonding and demonstrate an integrated optical architecture for realizing a compact strontium atomic clock. Our planar design includes twelve beams in two coaligned magnetooptical traps. These beams are directed above the chip to intersect at a central location with diameters as large as 1 cm. Our design also includes two copropagating beams at lattice and clock wavelengths. These beams emit collinearly and vertically to probe the center of the magnetooptical trap, where they will have diameters of ≈100 µm. With these devices we demonstrate that our integrated photonic platform is scalable to an arbitrary number of beams, each with different wavelengths, geometries, and polarizations.

R. BustosRamirez, C. Shirpurkar, S. Pericherla, L. R. Trask, T. C. Briles, J. R. Stone, S.P. Yu, A. Bhardwaj, G. E. Hoefler, S. B. Papp, and P. J. Delfyett, "Synchronization of ElectroOptically Modulated Kerr Soliton to a ChipScale ModeLocked Laser PIC via Regenerative Harmonic Injection Locking", J. Light. Technol. 40, 1742–1748 (2022), DOI: 10.1109/JLT.2021.3135235
An InPbased modelocked laser photonic integrated circuit with a repetition rate of 10 GHz is optically synchronized to a SiN microresonatorbased dissipative Kerr soliton with a rep etition rate of 305 GHz. The synchronization is achieved through regenerative harmonic injection locking assisted with electrooptic division which results in an optical frequency division factor of 18. The repetition rate of the dissipative Kerr soliton is stabilized through electrooptic division and transferred to the modelocked laser, where we measure a fractional frequency instability in the repetition rate of 10−10 at 1 s with a 1/τ trend. Furthermore, we also stabilize the repetition rate of the dissipative Kerr soliton using the modelocked laser’s repetition rate beat as a feedback point.

J. A. Black, G. Brodnik, H. Liu, S.P. Yu, D. R. Carlson, J. Zang, T. C. Briles, and S. B. Papp, "Opticalparametric oscillation in photoniccrystal ring resonators", Optica 9, 1183–1189 (2022), DOI: 10.1364/OPTICA.469210
Bydesign access to laser wavelength, especially with integrated photonics, is critical to advance quantum sensors, such as optical clocks and quantuminformation systems, and open opportunities in optical communication. Semiconductorlaser gain provides exemplary efficiency and integration but merely in developed wavelength bands. Alternatively, nonlinear optics requires control of phase matching, but the principle of nonlinear conversion of a pump laser to a designed wavelength is extensible. We report on laserwavelength access by versatile customization of opticalparametric oscillation (OPO) with a photoniccrystal ring resonator (PhCR). Leveraging the exquisite control of laser propagation provided by a photonic crystal in a travelingwave ring resonator, we enable OPO generation across a wavelength range of 1234–2093 nm with a 1550nm pump and 1016–1110 nm with a 1064nm pump. Moreover, our platform offers pumptosideband conversion efficiency of >10% and negligible additive opticalfrequency noise across the output range. From laser design to simulation of nonlinear dynamics, we use a Lugiato–Lefever framework that predicts the system characteristics, including bidirectional OPO generation in the PhCR and conversion efficiency in agreement with our observations. Our experiments introduce broadband lasers by design with PhCR OPOs, providing critical functionalities in integrated photonics.

K. Liu, J. H. Dallyn, G. M. Brodnik, A. Isichenko, M. W. Harrington, N. Chauhan, D. Bose, P. A. Morton, S. B. Papp, R. O. Behunin, D. Blumenthal, "Photonic circuits for laser stabilization with integrated ultrahigh Q and Brillouin laser resonators", APL Photonics 7, 096104, DOI: 10.1063/5.0091686
The integration of stabilized lasers, sources that generate spectrally pure light, will provide compact, lowcost solutions for applications including quantum information sciences, precision navigation and timing, metrology, and highcapacity fiber communications. We report a significant advancement in this field, demonstrating stabilization of an integrated waveguide Brillouin laser to an integrated waveguide reference cavity, where both resonators are fabricated using the same CMOScompatible integration platform. We demonstrate reduction of the free running Brillouin laser linewidth to a 292 Hz integral linewidth and carrier stabilization to a $4.9 \times 10^{−13}$ fractional frequency at 8 ms reaching the cavityintrinsic thermorefractive noise limit for frequencies down to 80 Hz. We achieve this level of performance using a pair of $56.4 \times 10^{6}$ quality factor $Si_{3}N_{4}$ waveguide ringresonators that reduce the highfrequency noise by the nonlinear Brillouin process and the lowfrequency noise by Pound–Drever–Hall locking to the ultralow loss resonator. These results represent an important step toward integrated stabilized lasers with reduced sensitivity to environmental disturbances for atomic, molecular, and optical physics (AMO), quantum information processing and sensing, and other precision scientific, sensing, and communications applications.

A. Quinn, J. Metzner, J. Muldoon, I. Moore, S. Brudney, S. Das, D. Allcock, Y. Joglekar, "Observing superquantum correlations across the exceptional point in a single, twolevel trapped ion", arXiv:2304.12413, DOI: 10.48550/arXiv.2304.12413
Quantum theory provides rules governing much of the microscopic world, and among its counterintuitive consequences are correlations that exceed the bounds from local, classical theories. In twolevel quantum systems  qubits  unitary dynamics theoretically limit these spatiotemporal quantum correlations, called Bell/ClauserHornShimonyHolt or LeggettGarg inequalities, to $2 \sqrt{2}$ or 1.5 respectively. Experiments with stateoftheart qubits have approached the spatial, Bell and temporal, LeggettGarg quantum correlation bounds. Here, using a dissipative, trapped $^{40}Ca^{+}$ ion governed by a twolevel, nonHermitian Hamiltonian, we observe temporal correlation values up to 1.703(4) for the LeggettGarg parameter $K_3$, clearly exceeding the hitherto inviolable Lüder's bound of 1.5. These excesses occur across the exceptional point of the paritytime symmetric Hamiltonian responsible for the qubit's nonunitary, coherent dynamics. Distinct evolution speeds for antipodal qubit states, which violate the unified (MendelstamTamm or MargolusLevitin) bound $\tau_{τQSL}$ for the transit time based on quantum speed limit, result in the superquantum $K_3$ values observed over a wide parameter range. Our results demonstrate that postselected, coherent dynamics of nonHermitian Hamiltonians pave the way for enhanced quantum correlations that exceed protocols based on unitary or dissipative dynamics.

D. Wineland, “Trapped ions meet quantum information processing, one perspective”, Proceedings of the 28th Solvay Conference on Physics: The Physics of Quantum Information, May 19 – 21, 2022, Brussels, Belgium. Ed. by David Gross, Alexander Sevrin, and Peter Zoller, World Scientific Publishing Co. pp. 32  45, 2023, DOI: 10.1142/9789811274855_0001

N. Segev and D. Wineland, "How to Catch an Atom: Tales on TimeTelling and Future Applications", Front. Young Minds 11:857992 (2023), DOI: 10.3389/frym.2023.857992

O. RubiesBigorda, S. Ostermann, and S. Yelin, "Characterizing superradiant dynamics in atomic arrays via a cumulant expansion approach", Phys. Rev. Research 5, 013091, DOI: 10.1103/PhysRevResearch.5.013091
Ordered atomic arrays with subwavelength lattice spacing emit light collectively. For fully inverted atomic arrays, this results in an initial burst of radiation and a fast buildup of coherences between the atoms at initial times. Based on a cumulant expansion of the equations of motion, we derive exact analytical expressions for the emission properties and numerically analyze the full manybody problem resulting in the collective decay process for unprecedented system sizes of up to a few hundred atoms. We benchmark the cumulant expansion approach and show that it correctly captures the cooperative dynamics resulting in superradiance. For fully inverted arrays, this allows us to extract the scaling of the superradiant peak with particle number. For partially excited arrays where no coherences are shared among atoms, we also determine the critical number of excitations required for the emergence of superradiance in one and twodimensional geometries. In addition, we study the robustness of superradiance in the case of nonunit filling and position disorder.

O. RubiesBigorda, S. Ostermann, and S. Yelin, "Dynamic population of multiexcitation subradiant states in incoherently excited atomic arrays", Phys. Rev. A 107, L051701, DOI: 10.1103/PhysRevA.107.L051701
The deterministic generation of multiexcitation subradiant states proves to be challenging. Here, we present a viable path towards their transient generation in finitesized ordered arrays of dipoledipole coupled quantum emitters, based on incoherent driving of the atomic ensemble. In particular, we show that a maximal coupling to longlived subradiant states is achieved if only half of the atoms are initially excited. We characterize the nature of the resulting states by calculating the dynamic fluorescence spectrum of the emitted light. Finally, we elucidate the role of coherent interactions during the decay process of sufficiently dense atomic arrays, which result in a coherently driven radiation burst that leads to a subsequent reduction of the chances to prepare multiexcitation subradiant states.

H. Ma, O. RubiesBigorda, S. Yelin, "Superradiance and subradiance in a gas of twolevel atoms", arXiv:2205.15255, DOI: arxiv.org/abs/2205.15255
Cooperative effects describe atomic ensembles with exchange of photonic excitations, such as dipoledipole interactions. As a particular example, superradiance arises from spontaneous emission when this exchange leads to constructive interference of the emitted photons. Here, we introduce an integrated method for studying cooperative radiation in manybody systems. This method, which allows to study extended systems with arbitrarily large number of particles can be formulated by an effective, nonlinear, twoatom master equation that describes the dynamics using a closed form which treats single and manybody terms on an equal footing. We apply this method to a homogeneous gas of initially inverted twolevel atoms, and demonstrate the appearance of both superradiance and subradiance, identifying a manybody coherence term as the source of these cooperative effects. We describe the manybody induced broadening  which is analytically found to scale with the optical depth of the system  and light shifts, and distinguish spontaneous effects from induced ones. In addition, we theoretically predict the timedependence of subradiance, and the phase change of the radiated field during the cooperative decay.

H. Ma, S. Yelin, "Collective Lamb Shift and Spontaneous Emission of A Dense Atomic Gas", arxiv.org/abs/2305.01865, DOI: 10.48550/arXiv.2305.01865
Finding a comprehensive and general description of the collective Lamb shift and cooperative broadening in a radiatively interacting system is a longstanding open question. Both, energy levels and decay rates, are modified by the exchange of real and virtual photons making up the dipoledipole interaction. We introduce a method to theoretically study weaklydriven, lowexcited ensembles of twolevel atoms and obtain an analytic description of the collective Lamb shift and collective decay rate via a selfconsistent formalism including multiple scattering. We predict the dependency of these quantities, as measurables, on system parameters: the number density of the ensemble, the detuning of an external probe field, and the geometry of the sample.

F. Shah, T. Patti, O. RubiesBigorda, S. Yelin, "Quantum computing with subwavelength atomic arrays", Phys. Rev. A 109, 012613 (2024), DOI: 10.1103/PhysRevA.109.012613
Photonmediated interactions in subwavelength atomic arrays have numerous applications in quantum science. In this manuscript, we explore the potential of threelevel quantum emitters, or ``impurities" embedded in a twodimensional atomic array to serve as a platform for quantum computation. By exploiting the altered behavior of impurities as a result of the induced dipoledipole interactions mediated by subwavelength array, we implement a set of universal quantum gates consisting of the $\sqrt{iSWAP}$ and singlequbit rotations. We demonstrate that these gates have very high fidelities and coherence times, as long as the atoms remain within a proximal range. Finally, we implement quantum circuits leading to the generation of the maximally entangled twoqubit Bell states, as well as the entangled threequbit GHZ state. These findings establish subwavelength emitter arrays as an alternative platform for quantum computation and quantum simulation.

R. Araiza Bravo, K. Najafi, T. Patti, X. Gao, S. Yelin, "Universal Quantum Perceptrons for Quantum Machine Learning", arxiv.org/abs/2211.07075, DOI: 10.48550/arXiv.2211.07075
Quantum neuromorphic computing (QNC) is a subfield of quantum machine learning (QML) that capitalizes on inherent system dynamics. As a result, QNC can run on contemporary, noisy quantum hardware and is poised to realize challenging algorithms in the near term. One key element yet to be added to QNC is the characterization of the requisite dynamics for universal quantum neuromorphic computation. We address this issue by proposing a quantum equivalent to the classical perceptron, a simple mathematical model for a neuron that is the building block of various machine learning architectures. We introduce a quantum perceptron (QP) based on the analog dynamics of interacting qubits with tunable coupling constants. By adding tunable singlequbit rotations to the QP, we demonstrate that a QP can realize universal quantum computation, which contrasts sharply with the limited computational complexity of a single classical perceptron. We show that QPs are analogous to variational quantum algorithms (VQAs) familiar to the quantum machine learning community. We derive the quantum neural tangent kernel of a QP and compare the QP's trainability to the trainability of other VQAs. We discuss the advantages and drawbacks of kernel formalism. Finally, we demonstrate the effectiveness of QPs by applying them to numerous QML problems, including calculating the inner products between quantum states, entanglement witnessing, and quantum metrology.

C. Overstreet, J. Curti, M. Kim, P. Asenbaum, M. Kasevich, F. Giacomini, "Inference of gravitational field superposition from quantum measurements", Phys. Rev. D 108, 084038 (2023), DOI: 10.1103/PhysRevD.108.084038
Experiments are beginning to probe the interaction of quantum particles with gravitational fields beyond the uniformfield regime. In nonrelativistic quantum mechanics, the gravitational field in such experiments can be written as a superposition state. We empirically demonstrate that alternative theories of gravity can avoid gravitational superposition states only by decoupling the gravitational field energy from the quantum particle's time evolution. Furthermore, such theories must specify a preferred quantum reference frame in which the equations of motion are valid. To the extent that these properties are theoretically implausible, recent experiments provide indirect evidence that gravity has quantum features. Proposed experiments with superposed gravitational sources would provide even stronger evidence that gravity is nonclassical.

J. Combes and A. Lund, "Homodyne measurement with a Schrödinger cat state as a local oscillator", Phys. Rev. A 106, 063706 (2022), DOI: 10.1103/PhysRevA.106.063706
Homodyne measurements are a widely used quantum measurement. Using a coherent state of large amplitude as the local oscillator, it can be shown that the quantum homodyne measurement limits to a field quadrature measurement. In this work, we give an example of a general idea: injecting nonclassical states as a local oscillator can lead to nonclassical measurements. Specifically, we consider injecting a superposition of coherent states, a Schrödinger cat state, as a local oscillator. We derive the Kraus operators and the positive operatorvalued measure in this situation.

B. Hauer, J. Combes, J. Teufel, "Nonlinear Sideband Cooling to a Cat State of Motion", Phys. Rev. Lett. 130, 213604 (2023), DOI: 10.1103/PhysRevLett.130.213604
The ability to prepare a macroscopic mechanical resonator into a quantum superposition state is an outstanding goal of cavity optomechanics. Here, we propose a technique to generate cat states of motion using the intrinsic nonlinearity of a dispersive optomechanical interaction. By applying a bichromatic drive to an optomechanical cavity, our protocol enhances the inherent secondorder processes of the system, inducing the requisite twophonon dissipation. We show that this nonlinear sideband cooling technique can dissipatively engineer a mechanical resonator into a cat state, which we verify using the full Hamiltonian and an adiabatically reduced model. While the fidelity of the cat state is maximized in the singlephoton, strongcoupling regime, we demonstrate that Wigner negativity persists even for weak coupling. Finally, we show that our cat state generation protocol is robust to significant thermal decoherence of the mechanical mode, indicating that such a procedure may be feasible for nearterm experimental systems.

A. Kyle, C. Rau, W. Warfield, A. Kwiatkowski, J. Teufel, K. Lehnert, T. Dennis, [Combes Group] "Optically Distributing Remote Twonode Microwave Entanglement using Doubly Parametric Quantum Transducers", arXiv:2211.09762, DOI: 10.48550/arXiv.2211.09762
Doublyparametric quantum transducers (DPTs), such as electrooptomechanical devices, show promise as quantum interconnects between the optical and microwave domains, thereby enabling long distance quantum networks between superconducting qubit systems. However, any transducer will inevitably introduce loss and noise that will degrade the performance of a quantum network. We explore how DPTs can be used to construct a network capable of distributing remote twomode microwave entanglement over an optical link by comparing fourteen different network topologies. The fourteen topologies we analyze consist of combinations of different transducer operations, entangled resources, and entanglement swapping measurements. For each topology, we derive a necessary and sufficient analytic threshold on DPT parameters that must be exceeded in order to distribute microwavemicrowave entanglement. We find that the thresholds are dependent on the given network topology, along with the available entanglement resources and measurement capabilities. In the high optical loss limit, which is relevant to realistic networks, we find that downconversion of each half of an optical twomode squeezed vacuum state is the most robust topology. Finally, we numerically evaluate the amount of microwavemicrowave entanglement generated for each topology using currently achievable values for DPT parameters, entangled resources, and swapping measurements, finding the encouraging result that several topologies are within reach of current experimental capabilities.

M. Nicotra, J. Shao, J. Combes, A. Theurkauf, P. Axelrad, LY Chih, M. J. Holland, A. Zozulya, C. LeDesma, K. Mehling, D. Z. Anderson, "Modeling and Control of Ultracold Atoms Trapped in an Optical Lattice: An Exampledriven Tutorial on Quantum Control", IEEE Control Systems Magazine ( Volume: 43, Issue: 1, 2023), DOI: 10.1109/MCS.2022.3216652
The laws of quantum mechanics capture the behavior of physical systems at the smallest observable spatiotemporal scales. By pushing systems to the very edge of physical limits, quantum technology has the potential to revolutionize the state of the art in a variety of domains, including metrology, communication, and computing. As the field continues its transition from a scientific curiosity to an engineering endeavor, experimental prototypes found in physics laboratories must be converted into reliable hardware platforms that operate in less sheltered contexts. This step (from quantum science to quantum engineering) represents a unique opportunity for the IEEE Control Systems Society to provide meaningful insights on how to systematically steer these systems to the desired operating point.

C. Luo, H. Zhang, V. P. W. Koh, J. D. Wilson, A. Chu, M. J. Holland, A. M. Rey, J. K. Thompson, "MomentumExchange Interactions in a Bragg Atom Interferometer Suppress Doppler Dephasing", Science 2024, 384 (6695), 551–556, DOI: 10.1126/science.adi1393
Large ensembles of lasercooled atoms interacting through infiniterange photonmediated interactions are powerful platforms for quantum simulation and sensing. Here we realize momentumexchange interactions in which pairs of atoms exchange their momentum states by collective emission and absorption of photons from a common cavity mode, a process equivalent to a spinexchange or XX collective Heisenberg interaction. The momentumexchange interaction leads to an observed alltoall Isinglike interaction in a matterwave interferometer. A manybody energy gap also emerges, effectively binding interferometer matterwave packets together to suppress Doppler dephasing in analogy to Mössbauer spectroscopy. The tunable momentumexchange interaction expands the capabilities of quantum interaction–enhanced matterwave interferometry and may enable the realization of exotic behaviors, including simulations of superconductors and dynamical gauge fields.

C. LeDesma, K. Mehling, J. Shao, J. D. Wilson, P. Axelrad, M. M. Nicotra, M. J. Holland, D. Z. Anderson, "A MachineDesigned Optical Lattice Atom Interferometer", arXiv:2305.17603, DOI: 10.48550/arXiv.2305.17603
Performing interferometry in an optical lattice formed by standing waves of light offers potential advantages over its freespace equivalents since the atoms can be confined and manipulated by the optical potential. We demonstrate such an interferometer in a one dimensional lattice and show the ability to control the atoms by imaging and reconstructing the wavefunction at many stages during its cycle. An acceleration signal is applied and the resulting performance is seen to be close to the optimum possible for the timespace area enclosed according to quantum theory. Our methodology of machine design enables the sensor to be reconfigurable on the fly, and when scaled up, offers the potential to make stateofthe art inertial and gravitational sensors that will have a wide range of potential applications.

J. T. Reilly, J. D. Wilson, S. B. Jäger, C. Wilson, M. J. Holland, "Optimal Generators for Quantum Sensing", Phys. Rev. Lett. 131, 150802 (2023), DOI: 10.1103/PhysRevLett.131.150802
We propose a computationally efficient method to derive the unitary evolution that a quantum state is most sensitive to. This allows one to determine the optimal use of an entangled state for quantum sensing, even in complex systems where intuition from canonical squeezing examples breaks down. In this paper we show that the maximal obtainable sensitivity using a given quantum state is determined by the largest eigenvalue of the quantum Fisher information matrix (QFIM) and, importantly, the corresponding evolution is uniquely determined by the coinciding eigenvector. Since we optimize the process of parameter encoding rather than focusing on state preparation protocols, our scheme is relevant for any quantum sensor. This procedure naturally optimizes multiparameter estimation by determining, through the eigenvectors of the QFIM, the maximal set of commuting observables with optimal sensitivity.

N. Hoghooghi, S. Xing, P. Chang, D. Lesko, A. Lind, G. Rieker, S. Diddams, “Broadband 1GHz Midinfrared Frequency Comb,” Light: Science & Applications 11, 17, (2022), DOI: 10.1038/s4137702200947w
Midinfrared (MIR) spectrometers are invaluable tools for molecular fingerprinting and hyperspectral imaging. Among the available spectroscopic approaches, GHz MIR dualcomb absorption spectrometers have the potential to simultaneously combine the highspeed, high spectral resolution, and broad optical bandwidth needed to accurately study complex, transient events in chemistry, combustion, and microscopy. However, such a spectrometer has not yet been demonstrated due to the lack of GHz MIR frequency combs with broad and full spectral coverage. Here, we introduce the first broadband MIR frequency comb laser platform at 1 GHz repetition rate that achieves spectral coverage from 3 to 13 $\mu m$. This frequency comb is based on a commercially available 1.56 $\mu µm$ modelocked laser, robust allfiber Er amplifiers and intrapulse difference frequency generation (IPDFG) of fewcycle pulses in $\chi^{(2)}$ nonlinear crystals. When used in a dual comb spectroscopy (DCS) configuration, this source will simultaneously enable measurements with μs time resolution, 1 GHz (0.03 cm$^{1}$) spectral point spacing and a full bandwidth of $>$ 5 THz ($>$ 166 cm$^{1}$) anywhere within the MIR atmospheric windows. This represents a unique spectroscopic resource for characterizing fast and nonrepetitive events that are currently inaccessible with other sources.

J. Metzner, A. Quinn, S. Brudney, I.D. Moore, S.C. Burd, D.J. Wineland, D.T.C Allcock, "Twomode squeezing and SU(1,1) interferometry with trapped ions", arXiv:2312.10847, DOI: 10.48550/arXiv.2312.10847
We experimentally implement circuits of one and two mode operations on two motional modes of a single trapped ion. This is achieved by implementing the required displacement, squeezing, twomode squeezing, and beamsplitter operations using oscillating electric potentials applied to the trap electrodes. The resulting electric fields drive the modes resonantly or parametrically without the need for optical forces. As a demonstration, we implement SU(2) and SU(1,1) interferometers with phase sensitivities near the CramérRao bound. We report a maximum sensitivity of a SU(2) interferometer within 0.67(5)dB of the standard quantum limit (SQL) as well as a single and twomode SU(1,1) sensitivity of 5.9(2)dB and 4.5(2)dB below the SQL respectively.

F.W. Knollmann, E. Clements, P.T. Callahan, M. Gehl, J.D. Hunker, T. Mahony, R. McConnell, R. Swint, C. SoraceAgaskar, I.L. Chuang, J. Chiaverini, and D. Stick, "Integrated photonic structures for photonmediated entanglement of trapped ions", arXiv:2401.06850 (2024), DOI: 10.48550/arXiv.2401.06850
Trapped atomic ions are natural candidates for quantum information processing and have the potential to realize or improve quantum computing, sensing, and networking. These applications often require the collection of individual photons emitted from ions into guided optical modes, in some cases for the production of entanglement between separated ions. Proofofprinciple demonstrations of such photon collection from trapped ions have been performed using highnumericalaperture lenses and singlemode fibers, but integrated photonic elements in iontrap structures offer advantages in scalability and manufacturabilty over traditional optics. In this paper we analyze structures monolithically fabricated with an ion trap for collecting single photons from ions, coupling them into integrated waveguides, and manipulating them via interference. We discuss practical considerations for realizing photonmediated entanglement between trapped ions using these waveguidebased devices.

A. Hattori, T. Sneh, M. Notaros, S. Corsetti, P.T. Callahan, D. Kharas, T. Mahony, R. McConnell, J. Chiaverini, and J. Notaros, "Integrated visiblelight polarization rotators and splitters for atomic quantum systems", Opt. Lett. 7, 1794 (2024), DOI: 10.1364/OL.509747
In this work, we design and experimentally demonstrate the first, to the best of our knowledge, integrated polarization splitters and rotators at blue wavelengths. We develop compact and efficient designs for both a polarization splitter and rotator at a 422nm wavelength, an important lasercooling transition for $^{88}$Sr$^{+}$ ions. These devices are fabricated in a 200mm waferscale process and experimentally demonstrated, resulting in a measured polarizationsplitter transverseelectric thruport coupling of 98.0\% and transversemagnetic tapport coupling of 77.6\% for a compact 16$\mu$mlong device and a polarizationrotator conversion efficiency of 92.2\% for a separate compact 111$\mu$mlong device. This work paves the way for more sophisticated integrated control of trappedion and neutralatom quantum systems.

S. Corsetti, A. Hattori, R. Swint, M. Notaros, G.N. West, T. Sneh, F. Knollmann, P.T. Callahan, T. Mahony, E.R. Clements, D. Kharas, C. SoraceAgaskar, R. McConnell, J. Chiaverini, and J. Notaros, "Integrated PolarizationDiverse Grating Emitters for TrappedIon Quantum Systems", Frontiers in Optics + Laser Science 2023, JTu7A.3 (2023), DOI: 10.1364/FIO.2023.JTu7A.3
We design and experimentally demonstrate the first pair of integrated TE and TM emitting gratings at a wavelength of 422nm, targeting the $5^{2}s_{1/2}5^{2}p_{1/2}$ transition of $^{88}$Sr$^{+}$ ions, to enable operations requiring diverse polarizations for integratedphotonicsbased trappedion quantum systems.

K. DeBry, J. SinananSingh, C.D. Bruzewicz, D. Reens, M.E. Kim, M.P. Roychowdhury, R. McConnell, I.L. Chuang, and J. Chiaverini, "Experimental Quantum Channel Discrimination Using Metastable States of a Trapped Ion", Phys. Rev. Lett. 131, 170602 (2023), DOI: 10.1103/PhysRevLett.131.170602
We present experimental demonstrations of accurate and unambiguous singleshot discrimination between three quantum channels using a single trapped $^{40}$Ca$^{+}$ ion. The three channels cannot be distinguished unambiguously using repeated single channel queries, the natural classical analogue. We develop techniques for using the sixdimensional D$_{5/2}$ state space for quantum information processing, and we implement protocols to discriminate quantum channel analogues of phase shift keying and amplitude shift keying data encodings used in classical radio communication. The demonstrations achieve discrimination accuracy exceeding 99\% in each case, limited entirely by known experimental imperfections.

T. G. Thurtell and A. Miyake, "Optimizing oneaxis twists for variational Bayesian quantum metrology", preprint arXiv.2212.12461, to appear in Phys. Rev. Research (2024), DOI: 10.48550/arXiv.2212.12461
Variational Bayesian quantum metrology is a promising avenue toward quantum advantage in sensing which optimizes both the state preparation (or encoding) and measurement (or decoding) procedures and takes prior information into account. For the sake of practical advantage, it is important to understand how effective various parametrized protocols are as well as how robust they are to the effects of complex noise, such as spatially correlated noise. First, we propose a new family of parametrized encoding and decoding protocols called arbitraryaxis twist ansatzes, and show that it can lead to a substantial reduction in the number of oneaxis twists needed to achieve a target estimation error. Second, using a polynomialsize tensor network algorithm, we analyze practical variational metrology beyond the symmetric subspace of a collective spin, and find that quantum advantage persists for shallowdepth ansatzes under realistic noise level.

V. Buchemmavari, S. Omanakuttan, YY. Jau, and I. Deutsch, "Entangling quantum logic gates in neutral atoms via the microwavedriven spinflip blockade", Phys. Rev. A 109, 012615 (2024), DOI: 10.1103/PhysRevA.109.012615
The Rydberg dipole blockade has emerged as the standard mechanism to induce entanglement between neutralatom qubits. In these protocols, laser fields that couple qubit states to Rydberg states are modulated to implement entangling gates. Here we present an alternative protocol to implement entangling gates via Rydberg dressing and a microwavefielddriven spinflip blockade [Y.Y. Jau et al., Nat. Phys. 12, 71 (2016)]. We consider the specific example of qubits encoded in the clock states of cesium. An auxiliary hyperfine state is optically dressed so that it acquires partial Rydberg character. It thus acts as a proxy Rydberg state, with a nonlinear light shift that plays the role of blockade strength. A microwavefrequency field coupling a qubit state to this dressed auxiliary state can be modulated to implement entangling gates. Logic gate protocols designed for the optical regime can be imported to this microwave regime, for which experimental control methods are more robust. We show that unlike the strong dipoleblockade regime usually employed in Rydberg experiments, going to a moderatespinflipblockade regime results in faster gates and smaller Rydberg decay. We study various regimes of operations that can yield highfidelity twoqubit entangling gates and characterize their analytical behavior. In addition to the inherent robustness of microwave control, we can design these gates to be more robust to laser amplitude and frequency noises at the cost of a small increase in Rydberg decay.

A. K. Forbes, P. D. Blocher, and I. H. Deutsch, "Modeling local decoherence of a spin ensemble using a generalized HolsteinPrimakoff mapping to a bosonic mode", preprint arXiv:2403.19801, DOI: 10.48550/arXiv.2403.19801
We show how the decoherence that occurs in an entangling atomic spinlight interface can be simply modeled as the dynamics of a bosonic mode. Although one seeks to control the collective spin of the atomic system in the permutationally invariant (symmetric) subspace, diffuse scattering and optical pumping are local, making an exact description of the manybody state intractable. To overcome this issue we develop a generalized HolsteinPrimakoff approximation for collective states which is valid when decoherence is uniform across a large atomic ensemble. In different applications the dynamics is conveniently treated as a Wigner function evolving according to a thermalizing diffusion equation, or by a FokkerPlanck equation for a bosonic mode decaying in a zero temperature reservoir. We use our formalism to study the combined effect of Hamiltonian evolution, local and collective decoherence, and measurement backaction in preparing nonclassical spin states for application in quantum metrology.

G. Krueper, L. Cohen and J. T. Gopinath, "New Cascaded Architecture for Classical and Quantum Multiparameter Sensing", arXiv:2304.08545 [quantph], Submitted to Optica Quantum (2024), DOI: 10.48550/arXiv.2304.08545
We present an innovative concept for quantumenhanced multiparameter optical phase sensing that can be implemented in free space, optical fiber or onchip. Our measurable phases are in series, or cascaded, enabling measurements as a function of position with only a single input and output. We have modeled up to 20 phases, and fitting shows nearlinear scaling of the power requirements for additional phases. This novel approach represents a new paradigm in multiparameter quantum metrology, and can be applied to remote sensing, communications, and geophysics.

Y. Xie, M. Nie, and S.W. Huang, "Inversedesigned broadband lowloss grating coupler on thick lithiumniobateoninsulator platform", Appl. Phys. Lett. 124, 051108 (2024), DOI: 10.1063/5.0184413
A grating coupler on 700nmthick Zcut lithiumniobateoninsulator platform with high coupling efficiency, large bandwidth, and high fabrication tolerance is designed and optimized by inverse design method. The optimized grating coupler is fabricated with a single set of ebeam lithography and etching process, and it is experimentally characterized to possess peak coupling efficiency of −3.8 dB at 1574.93 nm, 1 dB bandwidth of 71.7 nm, and 3 dB bandwidth of over 120 nm, respectively.

M. A. Bohman, S. G. Porsev, D. B. Hume, D. R. Leibrandt, M. S. Safronova, "Enhancing Divalent Optical Atomic Clocks with the 1S0↔3P2 Transition", Phys. Rev. A 108, 053120 (2023), DOI: 10.1103/PhysRevA.108.053120
Divalent atoms and ions with a singlet S ground state and triplet P excited state form the basis of many highprecision optical atomic clocks. Along with the metastable $^{3}P_{0}$ clock state, these atomic systems also have a nearby metastable 3P2 state. We investigate the properties of the electric quadrupole $^{1}S_{0} \leftrightarrow ^{3}P_{2}$ transition with a focus on enhancing already existing optical atomic clocks. In particular, we investigate the $^{1}S_{0} \leftrightarrow ^{3}P_{2}$ transition in $^{27}Al^{+}$ and calculate the differential polarizability, hyperfine effects, and other relevant atomic properties. We also discuss potential applications of this transition, notably that it provides two transitions with different sensitivities to systematic effects in the same species. In addition, we describe how the $^{1}S_{0} \leftrightarrow ^{3}P_{2}$ transition can be used to search for physics beyond the Standard Model and motivate investigation of this transition in other existing optical atomic clocks.

(One hundred sixteen authors including J. Doyle, J. Hogan, D. Hume, K. Lehnert, and S.W. Nam), "Quantum Sensors for High Energy Physics" arXiv:2311.01930 [hepex], DOI: 10.48550/arXiv.1803.11306
Report of the first workshop to identify approaches and techniques in the domain of quantum sensing that can be utilized by future High Energy Physics applications to further the scientific goals of High Energy Physics

J. Valencia, G. Iskander, N. V. Nardelli, D. R. Leibrandt, D. B. Hume, "Cryogenic sapphire optical reference cavity with crystalline coatings at 1×10−16 fractional instability" arXiv:2404.14310 [physics.optics], DOI: 10.48550/arXiv.2404.14310
The frequency stability of a laser locked to an optical reference cavity is fundamentally limited by thermal noise in the cavity length. These fluctuations are linked to material dissipation, which depends both on the temperature of the optical components and the material properties. Here, the design and experimental characterization of a sapphire optical cavity operated at 10 K with crystalline coatings at 1069 nm is presented. Theoretical estimates of the thermomechanical noise indicate a thermal noise floor below 4.5×10−18. Major technical noise contributions including vibrations, temperature fluctuations, and residual amplitude modulation are characterized in detail. The shortterm performance is measured via a threecornered hat analysis with two other cavitystabilized lasers, yielding a noise floor of 1×10−16. The longterm performance is measured against an optical lattice clock, indicating cavity stability at the level of 2×10−15 for averaging times up to 10,000 s.

C. Kiehl, T. S. Menon, S. Knappe, T. Thiele, C. A. Regal, "Correcting heading errors in optically pumped magnetometers through microwave interrogation", arXiv:2310.11017, DOI: 10.48550/arXiv.2310.11017
We demonstrate how to measure insitu for heading errors of optically pumped magnetometers in geomagnetic fields. For this, we implement microwavedriven Rabi oscillations and Ramsey interferometry on hyperfine transitions as two independent methods to detect scalar systematics of free induction decay (FID) signals. We showcase the wide applicability of this technique by operating in the challenging parameter regime of compact vapor cells with imperfect pumping and high buffer gas pressure. In this system, we achieve suppression of large inaccuracies arising from nonlinear Zeeman (NLZ) shifts by up to a factor of 10 to levels below 0.6 nT. In the Ramsey method we accomplish this, even in arbitrary magnetic field directions, by employing a hyperRamsey protocol and optical pumping with adiabatic power ramps. For the Rabi technique, this level of accuracy is reached, despite associated drivedependent shifts, by referencing Rabi frequency measurements to a complete atommicrowave coupling model that incorporates the microwave polarization structure.

E. P. Ruddy, Y. Jiang, N. E. Frattini, K. O. Quinlan, K. W. Lehnert, "Protecting backactionevading measurements from parametric instability", arXiv:2308.09168 (2023), DOI: 10.48550/arXiv.2308.09168
Noiseless measurement of a single quadrature in systems of parametrically coupled oscillators is theoretically possible by pumping at the sum and difference frequencies of the two oscillators, realizing a backactionevading (BAE) scheme. Although this would hold true in the simplest scenario for a system with pure threewave mixing, implementations of this scheme are hindered by unwanted higherorder parametric processes that destabilize the system and add noise. We show analytically that detuning the two pumps from the sum and difference frequencies can stabilize the system and fully recover the BAE performance, enabling operation at otherwise inaccessible cooperativities. We also show that the acceleration demonstrated in a weak signal detection experiment [PRX QUANTUM 4, 020302 (2023)] was only achievable because of this detuning technique.

K. Oliver, V. Borish, B. Wilcox, H. J. Lewandowski, "Implementation of the photovoice methodology in a projectbased upperdivision physics course", Phys. Rev. Phys. Educ. Res. 20, 010142, DOI: 10.1103/PhysRevPhysEducRes.20.010142
Photovoice is a type of participatory action research that aims to enable people to act as recorders and agents of change in their communities. When using the photovoice methodology, participants take photos in response to openended prompts and write short captions to accompany their photos. At the end of the photovoice process, participants engage in a focus group where they collectively determine some themes that their photos show, allowing them to cocreate the research being done. We implemented the photovoice methodology in a projectbased upperdivision physics course in which the students partnered with a company in the quantum industry to work on a realworld collaborative project. We present here an example of how photovoice can be used as part of a physics course with a focus on some preliminary results from the students' focus group. These results demonstrate that the focus group allowed us as researchers to gain new types of information from our students that we may not otherwise have learned, and that the students appreciated the photovoice process, particularly after engaging in the focus group activity.

V. Borish, H. J. Lewandowski, "Seeing quantum effects in experiments", Physical Review Physics Education Research 19, 020144 (2023), DOI: 10.1103/PhysRevPhysEducRes.19.020144
[This paper is part of the Focused Collection on Instructional labs: Improving traditions and new directions.] Quantum mechanics is a field often considered very mathematical, abstract, and unintuitive. One way some instructors are hoping to help familiarize their students with these complex topics is to have the students see quantum effects in experiments in undergraduate instructional labs. Here, we present results from an interview study about what it means to both instructors and students to see quantum effects in experiments. We focus on a popular set of quantum optics experiments and find that students believe they are observing quantum effects and achieving related learning goals by working with these experiments. Although it is not possible to see the quantum phenomena directly with their eyes, students point out different aspects of the experiments that contribute to them observing quantum effects. This often includes seeing the experimental results, sometimes in conjunction with interacting with or understanding part of the experiment. There is additional variation across student achievement of the various related learning goals, ranging from many of the students being excited about these experiments and making a connection between the mathematical theory and the experiments to only some of the students seeing a connection between these experiments and quantum technologies. This work can help instructors consider the importance and framing of quantum experiments and raises questions about when and how in the curriculum quantum experiments can be best utilized and how to make related learning goals available to all students.

K. Oliver, V. Borish, B. Wilcox, and H. J. Lewandowski, "The prettiest photos are the ones that have happy people in them: the use of photovoice in an upperdivision physics capstone project course", 2023 PERC Proceedings, p254 259 (2023) Notable Paper
Photovoice is a type of participatory action research that aims to enable people to act as recorders and agents of change in their communities. When using the photovoice methodology, participants take photos in response to openended prompts and write short captions to accompany their photos. At the end of the photovoice process, participants engage in a focus group where they collectively determine some themes that their photos show, allowing them to cocreate the research being done. We implemented the photovoice methodology in a projectbased upperdivision physics course in which the students partnered with a company in the quantum industry to work on a realworld collaborative project. We present here an example of how photovoice can be used as part of a physics course with a focus on some preliminary results from the students' focus group. These results demonstrate that the focus group allowed us as researchers to gain new types of information from our students that we may not otherwise have learned, and that the students appreciated the photovoice process, particularly after engaging in the focus group activity.

O. S. Burrow, R. J. Fasano, W. Brand, M. W. Wright, W. Li, A. D. Ludlow, E. Riis, P. F. Griffin, and A. S. Arnold, "Optimal binary gratings for multiwavelength magnetooptical traps", Opt. Express 31 40871 (2023), DOI: 10.1364/OE.498606
Grating magnetooptical traps are an enabling quantum technology for portable metrological devices with ultracold atoms. However, beam diffraction efficiency and angle are affected by wavelength, creating a singleoptic design challenge for laser cooling in two stages at two distinct wavelengths – as commonly used for loading, e.g., Sr or Yb atoms into optical lattice or tweezer clocks. Here, we optically characterize a wide variety of binary gratings at different wavelengths to find a simple empirical fit to experimental grating diffraction efficiency data in terms of dimensionless etch depth and period for various duty cycles. The model avoids complex 3D lightgrating surface calculations, yet still yields results accurate to a few percent across a broad range of parameters. Gratings optimized for two (or more) wavelengths can now be designed in an informed manner suitable for a wide class of atomic species enabling advanced quantum technologies.

J. L. Siegel, W. F. McGrew, Y. S. Hassan, C.C. Chen, K. Beloy, T. Grogan, X. Zhang, and A. D. Ludlow, "ExcitedBand Coherent Delocalization for Improved Optical Lattice Clock Performance", Phys. Rev. Lett. 132 133201 (2024), DOI: 10.1103/PhysRevLett.132.133201
We implement coherent delocalization as a tool for improving the two primary metrics of atomic clock performance: systematic uncertainty and instability. By decreasing atomic density with coherent delocalization, we suppress coldcollision shifts and twobody losses. Atom loss attributed to LandauZener tunneling in the ground lattice band would compromise coherent delocalization at low trap depths for our $^{171}$Yb atoms; hence, we implement for the first time delocalization in excited lattice bands. Doing so increases the spatial distribution of atoms trapped in the vertically oriented optical lattice by $\sim$ 7 times. At the same time, we observe a reduction of the coldcollision shift by 6.5(8) times, while also making inelastic twobody loss negligible. With these advantages, we measure the traplightinduced quenching rate and natural lifetime of the $^{3}$P$_{0}$ excited state as 5.7(7)\times$10^{4}$ $E_{r}^{1}$ s$^{1}$ and 19(2) s, respectively.

A. K. Rege, C. Smith, C. Monteleoni, T. Albash, "Hamiltonian learning using machine learning models trained with continuous measurements", Submitted to Physical Applied Review, April 2024, arXiv:2404.05526, DOI: 10.48550/arXiv.2404.05526
We build upon recent work on using Machine Learning models to estimate Hamiltonian parameters using continuous weak measurement of qubits as input. We consider two settings for the training of our model: (1) supervised learning where the weak measurement training record can be labeled with known Hamiltonian parameters, and (2) unsupervised learning where no labels are available. The first has the advantage of not requiring an explicit representation of the quantum state, thus potentially scaling very favorably to larger number of qubits. The second requires the implementation of a physical model to map the Hamiltonian parameters to a measurement record, which we implement using an integrator of the physical model with a recurrent neural network to provide a modelfree correction at every time step to account for small effects not captured by the physical model. We test our construction on a system of two qubits and demonstrate accurate prediction of multiple physical parameters in both the supervised and unsupervised context. We demonstrate that the model benefits from larger training sets establishing that it is in fact "learning", and we show robustness to errors in the assumed physical model by achieving accurate parameter estimation in the presence of unanticipated single particle relaxation.

P. T. Grochowski, H. Pichler, C. A. Regal, and O. RomeroIsart, "Quantum control of continuous systems via nonharmonic potential modulation", arXiv preprint, arxiv:2311.16819
We present a theoretical proposal for preparing and manipulating a state of a single continuousvariable degree of freedom confined to a nonharmonic potential. By utilizing optimally controlled modulation of the potential's position and depth, we demonstrate the generation of nonGaussian states, including Fock, GottesmanKitaev Preskill, multileggedcat, and cubicphase states, as well as the implementation of arbitrary unitaries within a selected twolevel subspace. Additionally, we propose protocols for singleshot orthogonal state discrimination and algorithmic cooling and analyze the robustness of this control scheme against noise. Since all the presented protocols rely solely on the precise modulation of the effective nonharmonic potential landscape, they are rel evant to several experiments with continuousvariable systems, including the motion of a single particle in an optical tweezer or lattice, or current in circuit quantum electrodynamics.

J. T. Young, E. Chaparro, A. P. Orioli, J. K. Thompson, A. M. Rey, "Engineering One Axis Twisting via a Dissipative Berry Phase Using Strong Symmetries", arxiv:2401.06222, DOI: 10.48550/arXiv.2401.06222
We show how a drivendissipative cavity coupled to a collective ensemble of atoms can dynamically generate metrologically useful spinsqueezed states. In contrast to other dissipative approaches, we do not rely on complex engineered dissipation or input states, nor do we require tuning the system to a critical point. Instead, we utilize a strong symmetry, a special type of symmetry that can occur in open quantum systems and emerges naturally in systems with collective dissipation, such as superradiance. This symmetry preserves coherence and allows for the accumulation of an atom numberdependent Berry phase which in turn creates spinsqueezed states via emergent oneaxis twisting dynamics. This work shows that it is possible to generate entanglement in an atomcavity resonant regime with macroscopic optical excitations of the system, going beyond the typical dispersive regime with negligible optical excitations often utilized in current cavity QED experiments.

W. R. Milner, S. Lannig, M. Mamaev, L. Yan, A. Chu, B. Lewis, M. N. Frankel, R. B. Hutson, A. M. Rey, J. Ye, "Coherent evolution of superexchange interaction in seconds long optical clock spectroscopy", arXiv:2402.13398, DOI: 10.48550/arXiv.2402.13398
Measurement science now connects strongly with engineering of quantum coherence, manybody states, and entanglement. To scale up the performance of an atomic clock using a degenerate Fermi gas loaded in a threedimensional optical lattice, we must understand complex manybody Hamiltonians to ensure meaningful gains for metrological applications. In this work, we use a near unity filled Sr 3D lattice to study the effect of a tunable FermiHubbard Hamiltonian. The clock laser introduces a spinorbit coupling spiral phase and breaks the isotropy of superexchange interactions, changing the Heisenberg spin model into one exhibiting XXZtype spin anisotropy. By tuning the lattice confinement and applying imaging spectroscopy we map out favorable atomic coherence regimes. With weak transverse confinement, both s and pwave interactions contribute to decoherence and atom loss, and their contributions can be balanced. At deep transverse confinement, we directly observe coherent superexchange interactions, tunable via onsite interaction and sitetosite energy shift, on the clock Ramsey fringe contrast over timescales of multiple seconds. This study provides a groundwork for using a 3D optical lattice clock to probe quantum magnetism and spin entanglement

C. Luo, H. Zhang, A. Chu, C. Maruko, A. M. Rey, J. K. Thompson, "Hamiltonian Engineering of collective XYZ spin models in an optical cavity: From oneaxis twisting to twoaxis counter twisting models", arxiv:2402.19429v1, DOI: 10.48550/arXiv.2402.19429
Quantum simulation using synthetic quantum systems offers unique opportunities to explore open questions in manybody physics and a path for the generation of useful entangled states. Nevertheless, so far many quantum simulators have been fundamentally limited in the models they can mimic. Here, we are able to realize an alltoall interaction with arbitrary quadratic Hamiltonian or effectively an infinite range tunable Heisenberg XYZ model. This is accomplished by engineering cavitymediated fourphoton interactions between 700 rubidium atoms in which we harness a pair of momentum states as the effective pseudo spin or qubit degree of freedom. Using this capability we realize for the first time the socalled twoaxis countertwisting model, an iconic XYZ collective spin model that can generate spinsqueezed states that saturate the Heisenberg limit bound. The versatility of our platform to include more than two relevant momentum states, combined with the flexibility of the simulated Hamiltonians by adding cavity tones opens rich opportunities for quantum simulation and quantum sensing in matterwave interferometers and other quantum sensors such as optical clocks and magnetometers.

S. Agarwal, E. Chaparro, D. Barberena, A. P. Orioli, G. Ferioli, S. Pancaldi, I. FerrierBarbut, A. Browaeys, A. M. Rey, "Directional superradiance in a driven ultracold atomic gas in freespace", arxiv:2403.15556, DOI: 10.48550/arXiv.2403.15556
Ultracold atomic systems are among the most promising platforms that have the potential to shed light on the complex behavior of manybody quantum systems. One prominent example is the case of a dense ensemble illuminated by a strong coherent drive while interacting via dipoledipole interactions. Despite being subjected to intense investigations, this system retains many open questions. A recent experiment carried out in a pencilshaped geometry reported measurements that seemed consistent with the emergence of strong collective effects in the form of a "superradiant" phase transition in free space, when looking at the light emission properties in the forward direction. Motivated by the experimental observations, we carry out a systematic theoretical analysis of the system's steadystate properties as a function of the driving strength and atom number, N. We observe signatures of collective effects in the weak drive regime, which disappear with increasing drive strength as the system evolves into a singleparticlelike mixed state comprised of randomly aligned dipoles. Although the steadystate features some similarities to the reported superradiant to normal nonequilibrium transition, also known as cooperative resonance fluorescence, we observe significant qualitative and quantitative differences, including a different scaling of the critical drive parameter (from N to $\sqrt{N}$. We validate the applicability of a meanfield treatment to capture the steadystate dynamics under currently accessible conditions. Furthermore, we develop a simple theoretical model that explains the scaling properties by accounting for interactioninduced inhomogeneous effects and spontaneous emission, which are intrinsic features of interacting disordered arrays in free space.

G. A. DomínguezCastro, T. Bilitewski, D. Wellnitz, A. M. Rey, L. Santos, "Relaxation in dipolar spin ladders: from pair production to falsevacuum decay", arxiv:2311.18091, DOI: 10.48550/arXiv.2311.18091
Ultracold dipolar particles pinned in optical lattices or tweezers provide an excellent platform for studying outofequilibrium quantum magnetism with dipolemediated couplings. Starting with an initial state with spins of opposite orientation in each of the legs of a ladder lattice, we show that spin relaxation displays an unexpected dependence on interleg distance and dipole orientation. This intricate dependence, stemming from the interplay between intra and interleg interactions, results in three distinct dynamical regimes: (i) ergodic, characterized by the fast relaxation towards equilibrium of correlated pairs of excitations generated at exponentially fast rates from the initial state; (ii) metastable, in which the state is quasilocalized in the initial state and only decays at exceedingly long timescales, resembling false vacuum decay; and, surprisingly, (iii) partiallyrelaxed, with coexisting fast partial relaxation and very longlived partial quasilocalization. Realizing these intriguing dynamics is within reach of current stateoftheart experiments in dipolar gases.

S. Hawaldar, P. Shahi, A. L. Carter, A. M. Rey, J. J. Bollinger, A. Shankar, "Bilayer crystals of trapped ions for quantum information processing", arxiv:2312.10681, DOI: 10.48550/arXiv.2312.10681
Trapped ion systems are a leading platform for quantum information processing, but they are currently limited to 1D and 2D arrays, which imposes restrictions on both their scalability and their range of applications. Here, we propose a path to overcome this limitation by demonstrating that Penning traps can be used to realize remarkably clean bilayer crystals, wherein hundreds of ions selforganize into two welldefined layers. These bilayer crystals are made possible by the inclusion of an anharmonic trapping potential, which is readily implementable with current technology. We study the normal modes of this system and discover salient differences compared to the modes of singleplane crystals. The bilayer geometry and the unique properties of the normal modes open new opportunities, in particular in quantum sensing and quantum simulation, that are not straightforward in singleplane crystals. Furthermore, we illustrate that it may be possible to extend the ideas presented here to realize multilayer crystals with more than two layers. Our work increases the dimensionality of trapped ion systems by efficiently utilizing all three spatial dimensions and lays the foundation for a new generation of quantum information processing experiments with multilayer 3D crystals of trapped ions.

N. Hoghooghi, P. Chang, S. Egbert, M. Burch, R. Shaik, P. Lynch, S. Diddams, G. B. Rieker, "Complete reactantstoproducts observation of a gasphase chemical reaction with broad, fast midinfrared frequency combs", arxiv:2307.07029, DOI: 10.48550/arXiv.2307.07029
Molecular diagnostics are a primary tool of modern chemistry, enabling researchers to map chemical reaction pathways and rates to better design and control chemical systems. Many chemical reactions are complex and fast, and existing diagnostic approaches provide incomplete information. For example, mass spectrometry is optimized to gather snapshots of the presence of many chemical species, while conventional laser spectroscopy can quantify a single chemical species through time. Here we optimize for multiple objectives by introducing a highspeed and broadband, midinfrared dual frequency comb absorption spectrometer. The optical bandwidth of $>$ 1000 cm$^{1}$ covers absorption fingerprints of many species with spectral resolution $<$ 0.03 cm1 to accurately discern their absolute quantities. Key to this advance are 1 GHz pulse repetition rate frequency combs covering the 35 $\mu$m region that enable microsecond tracking of fast chemical process dynamics. We demonstrate this system to quantify the abundances and temperatures of each species in the complete reactantstoproducts breakdown of 1,3,5trioxane, which exhibits a formaldehyde decomposition pathway that is critical to modern low temperature combustion systems. By maximizing the number of observed species and improving the accuracy of temperature and concentration measurements, this spectrometer advances understanding of chemical reaction pathways and rates and opens the door for novel developments such as combining highspeed chemistry with machine learning.

A. Aeppli, K. Kim, W. Warfield, M. S. Safronova, J. Ye, "A clock with 8×10−19 systematic uncertainty", arXiv:2403.10664, DOI: 10.48550/arXiv.2403.10664
We report an optical lattice clock with a total systematic uncertainty of $8.1 \times 10^{19}$ in fractional frequency units, representing the lowest uncertainty of any clock to date. The clock relies on interrogating the ultra narrow $^{1}S_{0} \rightarrow ^{3}P_{0}$ transition in a dilute ensemble of fermionic strontium atoms trapped in a verticallyoriented, shallow, onedimensional optical lattice. With $10^{5}$ atoms in WannierStark eigenstates of this lattice, we measure record atomic coherence time and measurement precision reaching below $1 \times 10^{19}$ [arXiv:2109.12238]. Such clock precision, together with imaging spectroscopy, enables precise control of collisional shifts as well as the lattice light shift [arXiv:2201.05909, arXiv:2210.16374]. To address two remaining large systematic effects, we measure the second order Zeeman coefficient on the least magnetically sensitive clock transition, and we precisely determine the 5s4d $^{3}D_{1}$ lifetime to reduce the dynamic black body radiation shift uncertainty. All other systematic effects have uncertainties below $1 \times 10^{19}$.

J. Arakawa, M. H. Zaheer, J. Eby, V. Takhistov, M. S. Safronova, "Bosenovae with QuadraticallyCoupled Scalars in Quantum Sensing Experiments", arXiv:2402.06736, DOI: 10.48550/arXiv.2402.06736
Ultralight dark matter (ULDM) particles of mass $m_{\phi} \le 1$ eV can form boson stars in DM halos. Collapse of boson stars leads to explosive bosenova emission of copious relativistic ULDM particles. In this work, we analyze sensitivity of terrestrial and spacebased experiments to detect such relativistic scalar ULDM particles interacting through quadratic couplings with Standard Model constituents, including electrons, photons and gluons. We highlight key differences with searches for linear ULDM couplings. Screening of ULDM with quadratic couplings near the surface of the Earth can significantly impact observations in terrestrial experiments, motivating future spacebased experiments. We demonstrate excellent ULDM discovery prospects, especially for quantum sensors, which can probe quadratic couplings orders below existing constraints by detecting bosenova events in the ULDM mass range $10^{23} eV \le m_{\phi} \le 10^{5} eV$. We also report updated constraints on quadratic couplings of ULDM in case it comprises cold DM.

V. Klüsener, S. Pucher, D. Yankelev, J. Trautmann, F. Spriestersbach, D. Filin, S. G. Porsev, M. S. Safronova, I. Bloch, S. Blatt, "Coherent excitation of a μHz scale optical magnetic quadrupole transition", arXiv:2401.03934, accepted to Phys. Rev. Lett. (2024), DOI: 10.48550/arXiv.2401.03934
We report on the coherent excitation of the ultranarrow $^{1}S_{0}$  $^{3}P_{2}$ magnetic quadrupole transition in $^{88}$Sr. By confining atoms in a state insensitive optical lattice, we achieve excitation fractions of 97(1)\% and observe linewidths as narrow as 58(1) Hz. With Ramsey spectroscopy, we find coherence times of 14(1) ms, which can be extended to 266(36) ms using a spinecho sequence. We determine the linewidth of the M2 transition to 24(7) $\mu$Hz, confirming longstanding theoretical predictions. These results establish an additional clock transition in strontium and pave the way for applications of the metastable $^{3}P_{2}$ state in quantum computing and quantum simulations.

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J. Arakawa, J. Eby, M. S. Safronova, V. Takhistov, M. H. Zaheer, "Detection of Bosenovae with Quantum Sensors on Earth and in Space", arXiv:2306.16468, DOI: 10.48550/arXiv.2306.16468
In a broad class of theories, the accumulation of ultralight dark matter (ULDM) with particles of mass 10$^{22}$ eV $<$ m$_\phi$ $<$ 1 eV leads the to formation of longlived bound states known as boson stars. When the ULDM exhibits selfinteractions, prodigious bursts of energy carried by relativistic bosons are released from collapsing boson stars in bosenova explosions. We extensively explore the potential reach of terrestrial and spacebased experiments for detecting transient signatures of emitted relativistic bursts of scalar particles, including ULDM coupled to photons, electrons, and gluons, capturing a wide range of motivated theories. For the scenario of relaxion ULDM, we demonstrate that upcoming experiments and technology such as nuclear clocks as well as spacebased interferometers will be able to sensitively probe orders of magnitude in the ULDM couplingmass parameter space, challenging to study otherwise, by detecting signatures of transient bosenova events. Our analysis can be readily extended to different scenarios of relativistic scalar particle emission.

S. G. Porsev, M. G. Kozlov, M. S. Safronova, "Contribution of negativeenergy states to multipolar polarizabilities of the Sr optical lattice clock", Phys. Rev. A 108, L051102 (2023), DOI: 10.1103/PhysRevA.108.L051102
We address the problem of lattice light shifts in the Sr clock caused by multipolar M1 and E2 atomfield interactions. We present a simple but accurate formula for the magneticdipole polarizability that takes into account the contributions of both the positive and negativeenergy states. We calculate the contribution of negativeenergy states to the M1 polarizabilities of the clock $^{1}S_{0}$ and $^{3}P_{0}$ states at the magic frequency. Taking these contributions into account, we obtain good agreement with the experimental results, explaining the major discrepancy between theory and experiment.

A. Banerjee, D. Budker, M. Filzinger, N. Huntemann, G. Paz, G. Perez, S. Porsev, M. Safronova, "Oscillating nuclear charge radii as sensors for ultralight dark matter", arXiv:2301.10784, DOI: 10.48550/arXiv.2301.10784
We show that coupling of ultralight dark matter (UDM) to quarks and gluons would lead to an oscillation of the nuclear charge radius for both the quantum chromodynamics (QCD) axion and scalar dark matter. Consequently, the resulting oscillation of electronic energy levels could be resolved with optical atomic clocks, and their comparisons can be used to investigate UDMnuclear couplings, which were previously only accessible with other platforms. We demonstrate this idea using the $^{2}S_{\frac{1}{2}}(F=0) \leftrightarrow ^{2}F_{\frac{7}{2}}(F=3)$ electric octupole and $^{2}S_{\frac{1}{2}}(F=0) \leftrightarrow ^{2}D_{\frac{3}{2}}(F=2)$ electric quadrupole transitions in $^{171}Yb^{+}$. Based on the derived sensitivity coefficients for these two transitions and a longterm comparison of their frequencies using a single trapped $^{171}Yb^{+}$ ion, we find bounds on the scalar UDMnuclear couplings and the QCD axion decay constant. These results are at a similar level compared to the tightest spectroscopic limits, and future investigations, also with other optical clocks, promise significant improvements.

A. Banerjee, G. Perez, M. Safronova, I. Savoray, A. Shalit, "The Phenomenology of Quadratically Coupled Ultra Light Dark Matter", J. High Energ. Phys. 2023, 42 (2023), DOI: 10.1007/JHEP10(2023)042
We discuss models of ultralight scalar Dark Matter (DM) with linear and quadratic couplings to the Standard Model (SM). In addition to studying the phenomenology of linear and quadratic interactions separately, we examine their interplay. We review the different experiments that can probe such interactions and present the current and expected future bounds on the parameter space. In particular, we discuss the scalar field solution presented in [A. Hees, O. Minazzoli, E. Savalle, Y. V. Stadnik and P. Wolf, Phys.Rev.D 98 (2018) 6, 064051], and extend it to theories that capture both the linear and the quadratic couplings of the Dark Matter (DM) field to the Standard Model (SM). Furthermore, we discuss the theoretical aspects and the corresponding challenges for natural models in which the quadratic interactions are of phenomenological importance.

YD. Tsai, J. Eby, J. Arakawa, D. Farnocchia, and M. S. Safronova, OSIRISREx constraints on local dark matter and cosmic neutrino profiles, JCAP 02, 029 (2024), DOI: 10.1088/14757516/2024/02/029
We derive purely gravitational constraints on dark matter and cosmic neutrino profiles in the solar system using asteroid (101955) Bennu. We focus on Bennu because of its extensive tracking data and highfidelity trajectory modeling resulting from the OSIRISREx mission. We find that the local density of dark matter is bound by $\rho_{\rm DM}\lesssim 3.3\times 10^{15}\;\rm kg/m^3 \simeq 6\times10^6\,\bar{\rho}_{\rm DM}$, in the vicinity of $\sim 1.1$ au (where $\bar{\rho}_{\rm DM}\simeq 0.3\;\rm GeV/cm^3$). We show that highprecision tracking data of solar system objects can constrain cosmic neutrino overdensities relative to the Standard Model prediction $\bar{n}_{\nu}$, at the level of $\eta\equiv n_\nu/\bar{n}_{\nu}\lesssim 1.7 \times 10^{11}(0.1 \;{\rm eV}/m_\nu)$ (Saturn), comparable to the existing bounds from KATRIN and other previous laboratory experiments (with $m_\nu$ the neutrino mass). These local bounds have interesting implications for existing and future directdetection experiments. Our constraints apply to all dark matter candidates but are particularly meaningful for scenarios including solar halos, stellar basins, and axion miniclusters, which predict overdensities in the solar system. Furthermore, introducing a DMSM longrange fifth force with a strength $\tilde{\alpha}_D$ times stronger than gravity, Bennu can set a constraint on $\rho_{\rm DM}\lesssim \bar{\rho}_{\rm DM}\left(6 \times 10^6/\tilde{\alpha}_D\right)$. These constraints can be improved in the future as the accuracy of tracking data improves, observational arcs increase, and more missions visit asteroids.

E. D. Caldwell, J.D. Deschenes, J. Ellis, W. C. Swann, B. K. Stuhl, H. Bergeron, N. R. Newbury, and L. C. Sinclair, "Quantumlimited optical time transfer for future geosynchronous links", Nature 618, 721 (2023), DOI: 10.1038/s41586023060325
The combination of optical time transfer and optical clocks opens up the possibility of largescale freespace networks that connect both groundbased optical clocks and future spacebased optical clocks. Such networks promise better tests of general relativity, darkmatter searches and gravitationalwave detection. The ability to connect optical clocks to a distant satellite could enable spacebased very long baseline interferometry, advanced satellite navigation8, clockbased geodesy and thousandfold improvements in intercontinental time dissemination. Thus far, only optical clocks have pushed towards quantumlimited performance. By contrast, optical time transfer has not operated at the analogous quantum limit set by the number of received photons. Here we demonstrate time transfer with near quantumlimited acquisition and timing at 10,000 times lower received power than previous approaches. Over 300 km between mountaintops in Hawaii with launched powers as low as 40 µW, distant sites are synchronized to 320 attoseconds. This nearly quantumlimited operation is critical for longdistance freespace links in which photons are few and amplification costly: at 4.0 mW transmit power, this approach can support 102 dB link loss, more than sufficient for future time transfer to geosynchronous orbits.

T. Dudley, J. Plusquellic, E. E. Tsiropoulou, J. Goldberg, D. Stick, D. Lobser. "ScatterGather DMA Performance Analysis within an SoCbased Control System for TrappedIon Quantum Computing", arxiv:2404.10619, DOI: 10.48550/arXiv.2404.10619
Scattergather dynamicmemoryaccess (SGDMA) is utilized in applications that require high bandwidth and low latency data transfers between memory and peripherals, where data blocks, described using buffer descriptors (BDs), are distributed throughout the memory system. The data transfer organization and requirements of a TrappedIon Quantum Computer (TIQC) possess characteristics similar to those targeted by SGDMA. In particular, the ion qubits in a TIQC are manipulated by applying control sequences consisting primarily of modulated laser pulses. These optical pulses are defined by parameters that are (re)configured by the electrical control system. Variations in the operating environment and equipment make it necessary to create and run a wide range of control sequence permutations, which can be well represented as BD regions distributed across the main memory. In this paper, we experimentally evaluate the latency and throughput of SGDMA on Xilinx radiofrequency SoC (RFSoC) devices under a variety of BD and payload sizes as a means of determining the benefits and limitations of an RFSoC system architecture for TIQC applications.

A. Vezvaee, N. Shitara, S. Sun, A. MontoyaCastillo, "Fourier Transform Noise Spectroscopy", to appear in npj Quantum Information, arxiv:2210.00386, DOI: 10.48550/arXiv.2210.00386
Spectral characterization of noise environments that lead to the decoherence of qubits is critical to developing robust quantum technologies. While dynamical decoupling offers one of the most successful approaches to characterize noise spectra, it necessitates applying large sequences of π pulses that increase the complexity and cost of the method. Here, we introduce a noise spectroscopy method that utilizes only the Fourier transform of free induction decay or spin echo measurements, thus removing the need for the application many π pulses. We show that our method faithfully recovers the correct noise spectra for a variety of different environments (including 1/ftype noise) and outperforms previous dynamical decoupling schemes while significantly reducing their experimental overhead. We also discuss the experimental feasibility of our proposal and demonstrate its robustness in the presence of statistical measurement error. Our method is applicable to a wide range of quantum platforms and provides a simpler path toward a more accurate spectral characterization of quantum devices, thus offering possibilities for tailored decoherence mitigation.

D. Kedar, J. Yu, E. Oelker, A. Staron, W. R. Milner, J. M. Robinson, T. Legero, F. Riehle, U. Sterr, and J. Ye, "Frequency stability of cryogenic silicon cavities with semiconductor crystalline coatings", Optica 10, 464 – 470 (2023), DOI: 10.1364/OPTICA.479462
Stateoftheart optical oscillators employing cryogenic reference cavities are limited in performance by the Brownian thermal noise associated with the mechanical dissipation of the mirror coatings. Recently, crystalline $Al_{1x}Ga_{x}As/GaAs$ coatings have emerged as a promising candidate for improved coating thermal noise. We present measurements of the frequency noise of two fully crystalline cryogenic reference cavities with $Al_{0.92}Ga_{0.08}As/GaAs$ optical coatings. We report on birefringent noise associated with anticorrelated frequency fluctuations between the polarization modes of the crystalline coatings and identify variables that affect its magnitude. Comparing the birefringent noise between the two cryogenic reference cavities reveals a phenomenological set of scalings with intracavity power and mode area. We implement an interrogation scheme that cancels this noise by simultaneous probing of both polarization modes. The residual noise remaining after this cancellation is larger than both cavities' thermal noise limits but still lower than the instabilities previously measured on equivalent resonators with dielectric coatings. Though the source of these noise mechanisms is unclear, we demonstrate that crystalline coatings can provide stability and sensitivity competitive with resonators employing dielectric coatings.

T. Tscherbul, J. Ye, and A. M. Rey, "Robust nuclear spin entanglement via dipolar interactions in polar molecules", Phys. Rev. Lett. 130, 143002 (2023), DOI: 10.1103/PhysRevLett.130.143002
We propose a general protocol for ondemand generation of robust entangled states of nuclear and/or electron spins of ultracold $^{1}\Sigma$ and $^{2}\Sigma$ polar molecules using electric dipolar interactions. By encoding a spin1/2 degree of freedom in a combined set of spin and rotational molecular levels, we theoretically demonstrate the emergence of effective spinspin interactions of the Ising and XXZ forms, enabled by efficient magnetic control over electric dipolar interactions. We show how to use these interactions to create longlived cluster and squeezed spin states.

J. J. Burau, P. Aggarwal, K. Mehling, and J. Ye, "Bluedetuned magnetooptical trap of molecules", Phys. Rev. Lett. 130, 193401 (2023). (Editor's Suggestion, Featured in Physics), DOI: 10.1103/PhysRevLett.130.193401
Direct laser cooling of molecules has reached a phasespace density exceeding 10−6 in optical traps but with rather small molecular numbers. To progress toward quantum degeneracy, a mechanism that combines subDoppler cooling and magnetooptical trapping would facilitate near unity transfer of ultracold molecules from the magnetooptical trap (MOT) to a conservative optical trap. Using the unique energy level structure of YO molecules, we demonstrate the first bluedetuned MOT for molecules that is optimized for both graymolasses subDoppler cooling and relatively strong trapping forces. This first subDoppler molecular MOT provides an increase of phasespace density by 2 orders of magnitude over any previously reported molecular MOT.

W. R. Milner, L. Yan, R. Hutson, C. Sanner, and J. Ye, "Highfidelity imaging of a band insulator in a threedimensional optical lattice clock", Phys. Rev. A 107, 063313 (2023), DOI: 10.1103/PhysRevA.107.063313
We report on the observation of a highdensity, band insulating state in a threedimensional optical lattice clock. Filled with a nuclearspinpolarized degenerate Fermi gas of $^{87}Sr$, the threedimensional (3D) lattice has one atom per site in the ground motional state, thus guarding against frequency shifts due to contact interactions. At this high density where the average distance between atoms is comparable to the probe wavelength, conventional imaging techniques at saturation intensity suffer from large systematic errors. To spatially probe frequency shifts in the clock and measure thermodynamic properties of this system, accurate imaging techniques at high optical depths are required. Using a combination of highly saturated fluorescence and absorption imaging, we confirm the density distribution in our 3D optical lattice in agreement with a single spin band insulating state. Combining our clock platform with this high filling fraction opens the door to studying new classes of longlived, manybody states arising from dipolar interactions.

J. Yu, S. Häfner, T. Legero, S. Herbers, D. Nicolodi, C. Y. Ma, F. Riehle, U. Sterr, D. Kedar, J. M. Robinson, E. Oelker, and J. Ye, "Excess noise and photoinduced effects in highly reflective crystalline mirror coatings", Phys. Rev. X 13, 041002 (2023), DOI: 10.1103/PhysRevX.13.041002
Thermodynamically induced length fluctuations of highreflectivity mirror coatings put a fundamental limit on sensitivity and stability of precision optical interferometers like gravitationalwave detectors and ultrastable lasers. The main contribution—Brownian thermal noise—is related to the mechanical loss of the coating material. $Al_{0.92}Ga_{0.08}As/GaAs$ crystalline mirror coatings are expected to reduce this limit. The first measurements of cryogenic silicon cavities revealed the existence of additional noise contributions exceeding the expected Brownian thermal noise. We describe a novel, nonthermal, photoinduced effect in birefringence that is most likely related to the recently discovered birefringence noise. Our studies of the dynamics and power dependence are an important step toward uncovering the underlying mechanisms. Averaging the anticorrelated birefringent noise results in a residual noise that is shown to be substantially different from Brownian thermal noise. To this end, we develop a new method for analyzing the coating noise in higherorder transversecavity modes, which makes it possible for the first time to determine the contribution of Brownian thermal noise to the total cavity noise. The new noise contributions must be considered carefully in precision interferometry experiments using similar coatings based on semiconductor materials.

D. Kedar, Z.B. Yao, I. Ryger, J. L. Hall, and J. Ye, "Synthetic FM triplets for AMfree precision laser stabilization and spectroscopy", Optica 11, 58 – 63 (2024), DOI: 10.1364/OPTICA.507655
The Pound–Drever–Hall (PDH) cavitylocking scheme has found prevalent uses in precision optical interferometry and laser frequency stabilization. A form of frequency modulation spectroscopy, PDH enjoys superior signaltonoise recovery, large acquisition dynamic range, wide servo bandwidth, and robust rejection of spurious effects. However, residual amplitude modulation at the signal frequency, while significantly suppressed, still presents an important concern for further advancing the stateoftheart performances. Here we present a simplified and improved scheme for PDH using an acoustooptic modulator to generate digital phase reference sidebands instead of the traditionally used electrooptic modulator approach. We demonstrate four key advantages: (1) the carrier and two modulation tones are individually synthesized and easily reconfigured, (2) robust and orthogonal control of the modulated optical field is applied directly to the amplitude and phase quadratures, (3) modulation synthesis, demodulation, and feedback are implemented in a selfcontained and easily reproducible electronic unit, and (4) superior active and passive control of residual amplitude modulation is achieved, especially when the carrier power is vanishingly low. These distinct merits stimulate new ideas on how we optimally enact PDH for a wide range of applications.

T. Langen, G. Valtolina, D. Wang, J. Ye, "Quantum state manipulation and science of ultracold molecules", Nature Phys., March 2024. (Invited review) 10.1038/s41567024024231, DOI: 10.48550/arXiv.2305.13445
An increasingly large variety of molecular species are being cooled down to low energies in recent years, and innovative ideas and powerful techniques continue to emerge to gain ever more precise control of molecular motion. In this brief review we focus our discussions on two widely employed cooling techniques that have brought molecular gases into the quantum regime: association of ultracold atomic gases into quantum gases of molecules and direct laser cooling of molecules. These advances have brought into reality our capability to prepare and manipulate both internal and external states of molecules quantum mechanically, opening the field of cold molecules to a wide range of scientific explorations.

J. Ye and P. Zoller, "Essay: quantum sensing with AMO platforms for fundamental physics", Phys. Rev. Lett. 132, 190001 (2024). (Invited Essay), DOI: 10.1103/PhysRevLett.132.190001
Atomic, molecular, and optical (AMO) physics has been at the forefront of the development of quantum science while laying the foundation for modern technology. With the growing capabilities of quantum control of many atoms for engineered manybody states and quantum entanglement, a key question emerges: what critical impact will the second quantum revolution with ubiquitous applications of entanglement bring to bear on fundamental physics? In this Essay, we argue that a compelling longterm vision for fundamental physics and novel applications is to harness the rapid development of quantum information science to define and advance the frontiers of measurement physics, with strong potential for fundamental discoveries. As quantum technologies, such as faulttolerant quantum computing and entangled quantum sensor networks, become much more advanced than today's realization, we wonder what doors of basic science can these tools unlock. We anticipate that some of the most intriguing and challenging problems, such as quantum aspects of gravity, fundamental symmetries, or new physics beyond the minimal standard model, will be tackled at the emerging quantum measurement frontier.

A. Cao, W. J. Eckner, T. Lukin Yelin, A. W. Young, S. Jandura, L. Yan, K. Kim, G. Pupillo, J. Ye, N. Darkwah Oppong, and A. M. Kaufman, "Multiqubit gates and 'Schrӧdinger cat' states in an optical clock", Nature, submitted (2024), DOI: 10.48550/arXiv.2402.16289
Manyparticle entanglement is a key resource for achieving the fundamental precision limits of a quantum sensor. Optical atomic clocks, the current stateoftheart in frequency precision, are a rapidly emerging area of focus for entanglementenhanced metrology. Augmenting tweezerbased clocks featuring microscopic control and detection with the highfidelity entangling gates developed for atomarray information processing offers a promising route towards leveraging highly entangled quantum states for improved optical clocks. Here we develop and employ a family of multiqubit Rydberg gates to generate "Schrödinger cat" states of the GreenbergerHorneZeilinger (GHZ) type with up to 9 optical clock qubits in a programmable atom array. In an atomlaser comparison at sufficiently short dark times, we demonstrate a fractional frequency instability below the standard quantum limit using GHZ states of up to 4 qubits. A key challenge to improving the optimal achievable clock precision with GHZ states is their reduced dynamic range. Towards overcoming this hurdle, we simultaneously prepare a cascade of varyingsize GHZ states to perform unambiguous phase estimation over an extended interval. These results demonstrate key building blocks for approaching Heisenberglimited scaling of optical atomic clock precision.

J. J. Burau, K. Mehling, M. D. Frye, M. J. Chen, P. Aggarwal, J. M. Hutson, and J. Ye, "Collisions of spinpolarized YO molecules for single partial waves", Phys. Rev. Lett., submitted (2024), DOI: 10.48550/arXiv.2404.06652
Efficient subDoppler laser cooling and optical trapping of YO molecules offer new opportunities to study collisional dynamics in the quantum regime. Confined in a crossed optical dipole trap, we achieve the highest phasespace density of $2.5 \times 10^{5}$ for a bulk lasercooled molecular sample. This sets the stage to study YOYO collisions in the microkelvin temperature regime, and reveal statedependent, singlepartialwave twobody collisional loss rates. We determine the partialwave contributions to specific rotational states (first excited N=1 and ground N=0) following two strategies. First, we measure the change of the collision rate in a spin mixture of N=1 by tuning the kinetic energy with respect to the p and dwave centrifugal barriers. Second, we compare loss rates between a spin mixture and a spinpolarized state in N=0. Using quantum defect theory with a partially absorbing boundary condition at short range, we show that the dependence on temperature for N=1 can be reproduced in the presence of a dwave or fwave resonance, and the dependence on a spin mixture for N=0 with a pwave resonance.

A. N. Carroll, H. Hirzler, C. Miller, D. Wellnitz, S. R. Muleady, J.Y. Lin, K. P. Zamarski, R. R.W. Wang, J. L. Bohn, A. M. Rey, and J. Ye, "Observation of generalized tJ spin dynamics with tunable dipolar interactions", Science, submitted (2024)., DOI: 10.48550/arXiv.2404.18916
Longrange and anisotropic dipolar interactions profoundly modify the dynamics of particles hopping in a periodic lattice potential. Here, we report the realization of a generalized tJ model with dipolar interactions using a system of ultracold fermionic molecules with spin encoded in the two lowest rotational states. We systematically explore the role of dipolar Ising and spinexchange couplings and the effect of motion on spin dynamics. The model parameters can be controlled independently, with dipolar couplings tuned by electric fields and motion regulated by optical lattices. Using Ramsey spectroscopy, we observed interactiondriven contrast decay that depends strongly both on the strength of the anisotropy between Ising and spinexchange couplings and on motion. These observations are supported by theory models established in different motional regimes that provide intuitive pictures of the underlying physics. This study paves the way for future exploration of kinetic spin dynamics and quantum magnetism with highly tunable molecular platforms in regimes challenging for existing numerical and analytical methods, and it could shed light on the complex behaviors observed in real materials.

C. Miller, A. N. Carroll, J.Y. Lin, H. Hirzler, H. Gao, H. Zhou, M. D. Lukin, J. Ye, "Twoaxis twisting using Floquetengineered XYZ spin models with polar molecules", Nature, submitted (2024), DOI: 10.48550/arXiv.2404.18913
Polar molecules confined in an optical lattice are a versatile platform to explore spinmotion dynamics based on strong, longrange dipolar interactions. The precise tunability of Ising and spinexchange interactions with both microwave and dc electric fields makes the molecular system particularly suitable for engineering complex manybody dynamics. Here, we used Floquet engineering to realize interesting quantum manybody systems of polar molecules. Using a spin encoded in the two lowest rotational states of ultracold KRb molecules, we mutually validated XXZ spin models tuned by a Floquet microwave pulse sequence against those tuned by a dc electric field through observations of Ramsey contrast dynamics, setting the stage for the realization of Hamiltonians inaccessible with static fields. In particular, we observed twoaxis twisting meanfield dynamics, generated by a Floquetengineered XYZ model using itinerant molecules in 2D layers. In the future, Floquetengineered Hamiltonians could generate entangled states for moleculebased precision measurement or could take advantage of the rich molecular structure for quantum simulation of multilevel systems.

P. M Jonah, S. Ostermann, H. Ritsch, S. Yelin, "Harnessing quantum emitter rings for efficient energy transport and trapping", Optica Quantum 2(2), DOI: 10.1364/OPTICAQ.510021
Efficient transport and harvesting of excitation energy under low light conditions is an important process in nature and quantum technologies alike. Here we formulate a quantum optics perspective to excitation energy transport in configurations of twolevel quantum emitters with a particular emphasis on efficiency and robustness against disorder. We study a periodic geometry of emitter rings with subwavelength spacing, where collective electronic states emerge due to nearfield dipole–dipole interactions. The system gives rise to collective subradiant states that are particularly suited to excitation transport and are protected from energy disorder and radiative decoherence. Comparing ring geometries with other configurations shows that the former are more efficient in absorbing, transporting, and trapping incident light. Because our findings are agnostic as to the specific choice of quantum emitters, they indicate general design principles for quantum technologies with superior photon transport properties and may elucidate potential mechanisms resulting in the highly efficient energy transport efficiencies in natural lightharvesting systems.

A. McClain Gomez, T. L. Patti, A. Anandkumar, S. F. Yelin, "NearTerm Distributed Quantum Computation using MeanField Corrections and Auxiliary Qubits", arXiv:2309.05693, DOI: 10.48550/arXiv.2309.05693
Distributed quantum computation is often proposed to increase the scalability of quantum hardware, as it reduces cooperative noise and requisite connectivity by sharing quantum information between distant quantum devices. However, such exchange of quantum information itself poses unique engineering challenges, requiring high gate fidelity and costly nonlocal operations. To mitigate this, we propose nearterm distributed quantum computing, focusing on approximate approaches that involve limited information transfer and conservative entanglement production. We first devise an approximate distributed computing scheme for the time evolution of quantum systems split across any combination of classical and quantum devices. Our procedure harnesses meanfield corrections and auxiliary qubits to link two or more devices classically, optimally encoding the auxiliary qubits to both minimize shorttime evolution error and extend the approximate scheme's performance to longer evolution times. We then expand the scheme to include limited quantum information transfer through selective qubit shuffling or teleportation, broadening our method's applicability and boosting its performance. Finally, we build upon these concepts to produce an approximate circuitcutting technique for the fragmented pretraining of variational quantum algorithms. To characterize our technique, we introduce a nonlinear perturbation theory that discerns the critical role of our meanfield corrections in optimization and may be suitable for analyzing other nonlinear quantum techniques. This fragmented pretraining is remarkably successful, reducing algorithmic error by orders of magnitude while requiring fewer iterations.

S. Ostermann, O. RubiesBigorda, V. Zhang, S. F. Yelin, "Breakdown of steadystate superradiance in extended driven atomic arrays", arxiv:2311.10824, DOI: 10.48550/arXiv.2311.10
Recent advances in generating well controlled dense arrangements of individual atoms in free space have generated interest in understanding how the extended nature of these systems influences superradiance phenomena. Here, we provide an indepth analysis on how spacedependent lightshifts and decay rates induced by dipoledipole interactions modify the steadystate properties of coherently driven arrays of quantum emitters. We characterize the steadystate phase diagram, with particular focus on the radiative properties in the steadystate. Interestingly, we find that diverging from the wellestablished Dicke paradigm of equal alltoall interactions significantly modifies the emission properties. In particular, the prominent quadratic scaling of the radiated light intensity with particle number in the steadystate  a hallmark of steadystate Dicke superradiance  is entirely suppressed, resulting in only linear scaling with particle number. We show that this breakdown of steadystate superradiance occurs due to the emergence of additional dissipation channels that populate not only superradiant states but also subradiant ones. The additional contribution of subradiant dark states in the dynamics leads to a divergence in the time scales needed to achieve steadystates. Building on this, we further show that measurements taken at finite times for extended atom ensembles reveal properties closely mirroring the idealized Dicke scenario.

Z. E. Chin, D. R. Leibrandt, and I. L. Chuang, “Quantum entanglement enables singleshot trajectory sensing for weakly interacting particles”, arXiv:2405.05888 (2024), DOI: 10.48550/arXiv.2405.05888
Sensors for mapping the trajectory of an incoming particle find important utility in experimental high energy physics and searches for dark matter. For a quantum sensing protocol that uses projective measurements on a multiqubit sensor array to infer the trajectory of an incident particle, we show that entanglement can dramatically reduce the particlesensor interaction strength $\theta$ required for perfect trajectory discrimination. Within an interval of $\theta$ above this reduced threshold, any unentangled sensor requires $\Theta(log(\frac{1}{\epsilon}))$ repetitions of the protocol to estimate the particle trajectory with $\epsilon$ error probability, whereas an entangled sensor can succeed with zero error in a single shot.

K. F. Chang, D M. B. Lesko, C Mashburn, P Chang, E Tsao, A J. Lind, and S A. Diddams, "Multiharmonic nearinfrared–ultraviolet dualcomb spectrometer," Opt. Lett. 49, 16841687 (2024), DOI: 10.1364/OL.515776
Dualcomb spectroscopy in the ultraviolet (UV) and visible would enable broad bandwidth electronic spectroscopy with unprecedented frequency resolution. However, there are significant challenges in generation, detection, and processing of dualcomb data that have restricted its progress in this spectral region. In this work, we leverage robust 1550 nm fewcycle pulses to generate frequency combs in the UV–visible. We combine these combs with a wavelength multiplexed dualcomb spectrometer and simultaneously retrieve 100 MHz combmoderesolved spectra over three distinct harmonics at 386, 500, and 760 nm. The experiments highlight the path to continuous dualcomb coverage spanning 200–750 nm, offering extensive access to electronic transitions in atoms, molecules, and solids.

N. Lordi, E. J. Tsao, A. J. Lind, S. A. Diddams, and J. Combes, "Quantum theory of temporally mismatched homodyne measurements with applications to opticalfrequencycomb metrology", Phys. Rev. A 109, 033722, March 2024, DOI: 10.1103/PhysRevA.109.033722
The fields of precision timekeeping and spectroscopy increasingly rely on opticalfrequencycomb interferometry. However, combbased measurements are not described by existing quantum theory because they exhibit both large mode mismatch and finitestrength local oscillators. To establish this quantum theory, we derive measurement operators for homodyne detection with arbitrary mode overlap. These operators are a combination of quadrature and intensitylike measurements, which inform a filter that maximizes the quadraturemeasurement signaltonoise ratio. Furthermore, these operators establish a foundation to extend frequencycomb interferometry to a wide range of scenarios, including metrology with nonclassical states of light.

P. Sekhar, C. Fredrick, D. R. Carlson, Z. L. Newman, S. A. Diddams, "20 GHz fiberintegrated femtosecond pulse and supercontinuum generation with a resonant electrooptic frequency comb", APL Photonics 1 November 2023; 8 (11): 116111, DOI: 10.1063/5.0165681
Frequency combs with mode spacing of 10–20 GHz are critical for increasingly important applications such as astronomical spectrograph calibration, highspeed dualcomb spectroscopy, and lownoise microwave generation. While electrooptic modulators and microresonators can provide narrowband comb sources at this repetition rate, a significant remaining challenge is a means to produce pulses with sufficient peak power to initiate nonlinear supercontinuum generation spanning hundreds of terahertz (THz) as required for selfreferencing. Here, we provide a simple, robust, and universal solution to this problem using offtheshelf polarizationmaintaining amplification and nonlinear fiber components. This fiberintegrated approach for nonlinear temporal compression and supercontinuum generation is demonstrated with a resonant electrooptic frequency comb at 1550 nm. We show how to readily achieve pulses shorter than 60 fs at a repetition rate of 20 GHz. The same technique can be applied to picosecond pulses at 10 GHz to demonstrate temporal compression by 9× and achieve 50 fs pulses with a peak power of 5.5 kW. These compressed pulses enable flat supercontinuum generation spanning more than 600 nm after propagation through multisegment dispersiontailored anomalousdispersion highly nonlinear fibers or tantala waveguides. The same 10 GHz source can readily achieve an octavespanning spectrum for selfreferencing in dispersionengineered silicon nitride waveguides. This simple allfiber approach to nonlinear spectral broadening fills a critical gap for transforming any narrowband 10–20 GHz frequency comb into a broadband spectrum for a wide range of applications that benefit from the high pulse rate and require access to the individual comb modes.

(Two hundred fifty three authors including J. Hogan and M. Safronova), "Terrestrial verylongbaseline atom interferometry: Workshop summary." AVS Quantum Science 6.2 (2024), DOI: 10.1116/5.0185291
This document presents a summary of the 2023 Terrestrial VeryLongBaseline Atom Interferometry Workshop hosted by CERN. The workshop brought together experts from around the world to discuss the exciting developments in largescale atom interferometer (AI) prototypes and their potential for detecting ultralight dark matter and gravitational waves. The primary objective of the workshop was to lay the groundwork for an international TVLBAI protocollaboration. This collaboration aims to unite researchers from different institutions to strategize and secure funding for terrestrial largescale AI projects. The ultimate goal is to create a roadmap detailing the design and technology choices for one or more kilometerscale detectors, which will be operational in the mid2030s. The key sections of this report present the physics case and technical challenges, together with a comprehensive overview of the discussions at the workshop together with the main conclusions.

D. Barberena, A. Chu, J.K. Thompson, A.M. Rey, "TradeOffs between Unitary and Measurement Induced Spin Squeezing in Cavity QED", September 26, 2023, arXiv:2309.15353, DOI: 10.48550/arXiv.2309.15353
We study the combined effects of measurements and unitary evolution on the preparation of spin squeezing in an ensemble of atoms interacting with a single electromagnetic field mode inside a cavity. We derive simple criteria that determine the conditions at which measurement based entanglement generation overperforms unitary protocols. We include all relevant sources of decoherence and study both their effect on the optimal spin squeezing and the overall size of the measurement noise, which limits the dynamical range of quantumenhanced phase measurements. Our conclusions are relevant for stateoftheart atomic clocks that aim to operate below the standard quantum limit.

J.A Muniz, D.J. Young, J.R.K. Cline, J.K. Thompson, "CavityQED Measurements of the Sr 87 Millihertz Optical Clock Transition and Determination of Its Natural Linewidth", Phys. Rev. Research 2021, 3 (2), 023152, DOI: 10.1103/PhysRevResearch.3.023152
We demonstrate the direct quantum nondemolition detection of a millihertz linewidth optical atomic transition. We observe the modification of the phase and amplitude of a probe field interacting with strontium atoms, which provides a direct spectroscopic signal to which a laser could be frequency stabilized. To investigate this measurement capability, we demonstrate an approach to determining the intrinsic natural lifetime of exceptionally longlived optical excited states. Such transitions are key to the performance of stateoftheart atomic clocks, have potential applications in searches for fundamental physics and gravitational wave detectors, as well as quantum manybody phenomena. Here, we determine the ratio of the challenging to measure and poorly known ultranarrow linewidth transition ($^{3}P_{0}$ to $^{1}S_{0}$ in $^{87}$Sr) to that of another narrow wellknown transition ($^{3}P_{1}$ to $^{1}S_{0}$) by coupling the two transitions to a single optical cavity and performing interleaved nondestructive measurements of the interaction strengths of the atoms with cavity modes near each transition frequency. We use this approach to determine the natural linewidth of the clock transition $^{3}P_{0}$ to $^{1}S_{0}$ in $^{87}$Sr to be $\gamma_{0}$/($2\pi$)= 1.35(3) mHz or $\tau$ = 118(3) s. The 30$\mu$Hz resolution implies that we could detect states with lifetimes just below 2 h, and with straightforward future improvements, we could detect states with lifetimes up to 15 h, using measurement trials that last only a few hundred milliseconds, eliminating the need for long storage times in optical potentials. This work opens the path to nondestructive direct spectroscopy of ultranarrow transition for continuous frequency measurements and laser stabilization.

S. S. Alam, V. E. Colussi, J. D. Wilson, J. T. Reilly, M. A. Perlin, and M. J. Holland, “Robust Quantum Sensing with Multiparameter Decorrelation”, arXiv 2405.07907, DOI: 10.48550/arXiv.2405.07907
The performance of a quantum sensor is fundamentally limited by noise. This noise is particularly damaging when it becomes correlated with the readout of a target signal, caused by fluctuations of the sensor's operating parameters. These uncertainties limit sensitivity in a way that can be understood with multiparameter estimation theory. We develop a new approach, adaptable to any quantum platform, for designing robust sensing protocols that leverages multiparameter estimation theory and machine learning to decorrelate a target signal from fluctuating offtarget ("nuisance") parameters. Central to our approach is the identification of informationtheoretic goals that guide a machine learning agent through an otherwise intractably large space of potential sensing protocols. As an illustrative example, we apply our approach to a reconfigurable optical lattice to design an accelerometer whose sensitivity is decorrelated from lattice depth noise. We demonstrate the effect of decorrelation on outcomes and Bayesian inferencing through statistical analysis in parameter space, and discuss implications for future applications in quantum metrology and computing.

G. M. Brodnik, H. Liu, D. R. Carlson, J. A. Black, S B. Papp, "Nanophotonic oscillators for laser conversion beyond an octave", arXiv preprint arXiv:2405.06746 (2024), DOI: 10.48550/arXiv.2405.06746
Many uses of lasers place the highest importance on access to specific wavelength bands. For example, mobilizing opticalatomic clocks for a leap in sensing requires compact lasers at frequencies spread across the visible and near infrared. Integrated photonics enables highperformance, scalable laser platforms, however, customizing lasergain media to support wholly new bands is challenging and often prohibitively mismatched in scalability to early quantumbased sensing and information systems. Here, we demonstrate a microresonator opticalparametric oscillator (OPO) that converts a pump laser to an output wave within a frequency span exceeding an octave. We achieve phase matching for oscillation by nanopatterning the microresonator to open a photoniccrystal bandgap on the mode of the pump laser. By adjusting the nanophotonic pattern and hence the bandgap, the ratio of output OPO wave frequency span to required pump laser tuning is more than 10,000. We also demonstrate tuning the oscillator in freespectralrange steps, more finely with temperature, and minimal additive frequency noise of the laserconversion process. Our work shows that nanophotonics offers control of laser conversion in microresonators, bridging phasematching of nonlinear optics and application requirements for laser designs.

J. Zang, H. Liu, T. C. Briles, S. B. Papp, "Foundry manufacturing of octavespanning microcombs", arXiv preprint arXiv:2404.13472 (2024), DOI: 10.48550/arXiv.2404.13472
Soliton microcombs provide a chipbased, octavespanning source for selfreferencing and optical metrology. We explore use of a siliconnitride integrated photonics foundry to manufacture octavespanning microcombs. By groupvelocity dispersion engineering with the waveguide crosssection, we shape the soliton spectrum for dispersivewave spectral enhancements at the frequencies for f2f selfreferencing. With the optimized waveguide geometry, we control the carrierenvelope offset frequency by adjusting the resonator radius. Moreover, we demonstrate the other considerations for octave microcombs, including models for soliton spectrum design, ultrabroadband resonator external coupling, lowloss edge couplers, and the nonlinear selfinteractions of fewcycle solitons. This design process permits highly repeatable creation of soliton microcombs optimized for pump operation less than 100 mW, an electronically detectable offset frequency, and high comb mode power for f2f detection. However, these design aspects must also be made compatible with the foundry fabrication tolerance of octave microcomb devices. Our experiments highlight the potential to manufacture a singlechip solution for an octavespanning microcomb, which is the central component of a compact microsystem for optical metrology.

A. R. Ferdinand, Z. Luo, S. Jammi, Z. Newman, G. Spektor, O. Koksal, P. B. Patel, D. Sheredy, W. Lunden, A. Rakholia, T. C. Briles, W. Zhu, M. M. Boyd, A. Agrawal, S. B. Papp, "Laser cooling 88Sr to microkelvin temperature with an integratedphotonics system", arXiv preprint arXiv:2404.13210 (2024), DOI: 10.48550/arXiv.2404.13210
We report on experiments generating a magnetooptical trap (MOT) of 88strontium (88Sr) atoms at microkelvin temperature, using integratedphotonics devices. With metasurface optics integrated on a fusedsilica substrate, we generate sixbeam, circularly polarized, counterpropagating MOTs on the blue broadline, 461 nm, and red narrowline, 689 nm, Sr cooling transitions without bulk optics. By use of a diverging beam configuration, we create up to 10 mm diameter MOT beams at the trapping location. To frequency stabilize and linewidth narrow the cooling lasers, we use fiberpackaged, integrated nonlinear waveguides to spectrally broaden a frequency comb. The ultracoherent supercontinuum of the waveguides covers 650 nm to 2500 nm, enabling phase locks of the cooling lasers to hertz level linewidth. Our work highlights the possibility to simplify the preparation of an ultracold 88Sr gas for an opticallattice clock with photonic devices. By implementing a timing sequence for control of the MOT lasers and the quadrupole magneticfield gradient, we collect atoms directly from a thermal beam into the blue MOT and continuously cool into a red MOT with dynamic detuning and intensity control. There, the red MOT temperature is as low as 2 μK and the overall transfer efficiency up to 16%. We characterize this sequence, including an intermediate red MOT with modulated detuning. Our experiments demonstrate an integrated photonics system capable of cooling alkalineearth gases to microkelvin temperature with sufficient transfer efficiencies for adoption in scalable optical clocks and quantum sensors.

Y. Jin, E. Lucas, J. Zang, T. Briles, I. Dickson, D. Carlson, S. B. Papp, "The bandgapdetuned excitation regime in photoniccrystal resonators", arXiv preprint arXiv:2404.11733 (2024), DOI: 10.48550/arXiv.2404.11733
Control of nonlinear interactions in microresonators enhances access to classical and quantum field states across nearly limitless bandwidth. A recent innovation has been to leverage coherent scattering of the intraresonator pump as a control of groupvelocity dispersion and nonlinear frequency shifts, which are precursors for the dynamical evolution of new field states. A uniform periodicity nanostructure addresses backscattering with one resonator mode, and pumping that mode enables universal phasematching for fourwave mixing with control by the bandgap. Yet, since nonlinearresonator phenomena are intrinsically multimode and exhibit complex modelocking, here we demonstrate a new approach to controlling nonlinear interactions by creating bandgap modes completely separate from the pump laser. We explore this bandgapdetuned excitation regime through generation of benchmark optical parametric oscillators (OPOs) and soliton microcombs. Indeed, we show that modelocked states are phase matched more effectively in the bandgapdetuned regime in which we directly control the modal Kerr shift with the bandgaps without perturbing the pump field. In particular, bandgapdetuned excitation enables an arbitrary control of backscattering as a versatile tool for modelocked state engineering. Our experiments leverage nanophotonic resonators for phase matching of OPOs and solitons, leading to control over threshold power, conversion efficiency, and emission direction that enable application advances in highcapacity signaling and computing, signal generation, and quantum sensing.

S. Jammi, A. R. Ferdinand, Z. Luo, Z. L. Newman, G. Spektor, J. Song, O. Koksal, A. V. Rakholia, W. Lunden, D. Sheredy, P. B. Patel, M. M. Boyd, W. Zhu, A. Agrawal, T. C. Briles, S. B. Papp, "Threedimensional, multiwavelength beam formation with integrated metasurface optics for Sr laser cooling", arXiv preprint arXiv:2402.08885 (2024), DOI: 10.48550/arXiv.2402.08885
We demonstrate the formation of a complex, multiwavelength, threedimensional laser beam configuration with integrated metasurface optics. Our experiments support the development of a compact Sr opticallattice clock, which leverages magnetooptical trapping on atomic transitions at 461 nm and 689 nm without bulk freespace optics. We integrate six, mmscale metasurface optics on a fusedsilica substrate and illuminate them with light from optical fibers. The metasurface optics provide full control of beam pointing, divergence, and polarization to create the laser configuration for a magnetooptical trap. We report the efficiency and integration of the threedimensional visible laser beam configuration, demonstrating the suitability of metasurface optics for atomic laser cooling.

G. Spektor, J. Zang, A. Dan, T. C. Briles, G. M. Brodnik, H. Liu, J. A. Black, D. R. Carlson, S. B. Papp, "Photonic bandgap microcombs at 1064 nm", APL Photonics 9.2 (2024), DOI: 10.1063/5.0191602
Microresonator frequency combs and their design versatility have revolutionized research areas from data communication to exoplanet searches. While microcombs in the 1550 nm band are well documented, there is interest in using microcombs in other bands. Here, we demonstrate the formation and spectral control of normaldispersion dark soliton microcombs at 1064 nm. We generate 200 GHz repetition rate microcombs by inducing a photonic bandgap of the microresonator mode for the pump laser with a photonic crystal. We perform the experiments with normaldispersion microresonators made from Ta$_{2}$O$_{5}$ and explore unique soliton pulse shapes and operating behaviors. By adjusting the resonator dispersion through its nanostructured geometry, we demonstrate control over the spectral bandwidth of these combs, and we employ numerical modeling to understand their existence range. Our results highlight how photonic design enables microcomb spectra tailoring across wide wavelength ranges, offering potential in bioimaging, spectroscopy, and photonicatomic quantum technologies.

C. Zhang, L. Chen, Z. Lin, J. Song, D. Wang, M. Li, O. Koksal, Z. Wang, G. Spektor, D. Carlson, H. J. Lezec, W. Zhu, S. Papp & A. Agrawal, "Tantalum pentoxide: a new material platform for highperformance dielectric metasurface optics in the ultraviolet and visible region", Light: Science & Applications 13.1 (2024): 23, DOI: 10.1038/s4137702301330z
Dielectric metasurfaces, composed of planar arrays of subwavelength dielectric structures that collectively mimic the operation of conventional bulk optical elements, have revolutionized the field of optics by their potential in constructing highefficiency and multifunctional optoelectronic systems on chip. The performance of a dielectric metasurface is largely determined by its constituent material, which is highly desired to have a high refractive index, low optical loss and wide bandgap, and at the same time, be fabrication friendly. Here, we present a new material platform based on tantalum pentoxide (Ta$_{2}$O$_{5}$) for implementing highperformance dielectric metasurface optics over the ultraviolet and visible spectral region. This widebandgap dielectric, exhibiting a high refractive index exceeding 2.1 and negligible extinction coefficient across a broad spectrum, can be easily deposited over large areas with good quality using straightforward physical vapor deposition, and patterned into highaspectratio subwavelength nanostructures through commonlyavailable fluorinegasbased reactive ion etching. We implement a series of highefficiency ultraviolet and visible metasurfaces with representative lightfield modulation functionalities including polarizationindependent highnumericalaperture lensing, spinselective hologram projection, and vivid structural color generation, and the devices exhibit operational efficiencies up to 80\%. Our work overcomes limitations faced by scalability of commonlyemployed metasurface dielectrics and their operation into the visible and ultraviolet spectral range, and provides a novel route towards realization of highperformance, robust and foundrymanufacturable metasurface optics.

S. Mittal, K. Adachi, N. E. Frattini, M. D. Urmey, SX. Lin, A. L. Emser, C. Metzger, L. Talamo, S. Dickson, D. Carlson, S. B. Papp, C. A. Regal, K. W. Lehnert, "Annealing reduces Si3N4 microwavefrequency dielectric loss in superconducting resonators", (2023), DOI: 10.48550/arXiv.2312.13504
The dielectric loss of silicon nitride (Si$_{3}$N$_{4}) limits the performance of microwavefrequency devices that rely on this material for sensing, signal processing, and quantum communication. Using superconducting resonant circuits, we measure the cryogenic loss tangent of either asdeposited or hightemperature annealed stoichiometric Si$_{3}$N$_{4}$ as a function of drive strength and temperature. The internal loss behavior of the electrical resonators is largely consistent with the standard tunneling model of twolevel systems (TLS), including damping caused by resonant energy exchange with TLS and by the relaxation of nonresonant TLS. We further supplement the TLS model with a selfheating effect to explain an increase in the loss observed in asdeposited films at large drive powers. Critically, we demonstrate that annealing remedies this anomalous powerinduced loss, reduces the relaxationtype damping by more than two orders of magnitude, and reduces the resonanttype damping by a factor of three. Employing infrared absorption spectroscopy, we find that annealing reduces the concentration of hydrogen in the Si$_{3}$N$_{4}$, suggesting that hydrogen impurities cause substantial dissipation..

J. Ramette, J. Sinclair, and V. Vuletić, "Counterfactual carving exponentially improves entangledstate fidelity", submitted to Phys. Rev. Lett. (1/2024), arXiv:2401.11407, DOI: 10.48550/arXiv.2401.11407
We propose a new method, "counterfactual" carving, that uses the "nojump" evolution of a probe to generate entangled manybody states of high fidelity. The probe is coupled to a target ensemble of qubits and engineered to exponentially decay at a rate depending on the target collective spin, such that postselecting on observing no probe decay precisely removes select fasterdecaying spin components. When probe and Nqubit target interact via a cavity mode of cooperativity C, counterfactual carving generates entangled states with infidelities of e−C/N, an exponential improvement over previous carving schemes. Counterfactual carving can generate complex entangled states for applications in quantum metrology and quantum computing.

G. Wang, W. Xu, C. Li, V. Vuletić, and P. Cappellaro, "Individualatom control in array through phase modulation", submitted to Phys. Rev. X (10/2023), arXiv:2310.19741, DOI: 10.48550/arXiv.2310.19741
Performing parallel gate operations while retaining low crosstalk is an essential step in transforming neutral atom arrays into powerful quantum computers and simulators. Tightly focusing control beams in small areas for crosstalk suppression is typically challenging and can lead to imperfect polarization for certain transitions. We tackle such a problem by introducing a method to engineer single qubit gates through phasemodulated continuous driving. Distinct qubits can be individually addressed to high accuracy by simply tuning the modulation parameters, which significantly suppresses crosstalk effects. When arranged in a lattice structure, individual control with optimal crosstalk suppression is achieved. With the assistance of additional addressing light or multiple modulation frequencies, we develop two efficient implementations of parallelgate operations. Our results pave the way to scaling up atomarray platforms with lowerror parallelgate operations, without requiring complicated wavefront design or highpower laser beams.

C. Shu, S. Colombo, Z. Li, A. Adiyatullin, E. Mendez, E. PedrozoPeñafiel, and V. Vuletić, "Increased AtomCavity Coupling through CoolingInduced Atomic Reorganization", submitted to Phys. Rev. Lett. (10/2023), arXiv:2310.17090, DOI: 10.48550/arXiv.2310.17090
The strong coupling of atoms to optical cavities can improve optical lattice clocks as the cavity enables metrologically useful collective atomic entanglement and highfidelity measurement. To this end, it is necessary to cool the ensemble to suppress motional broadening, and advantageous to maximize and homogenize the atomcavity coupling. We demonstrate resolved Raman sideband cooling via the cavity as a method that can simultaneously achieve both goals. In 200 ms, we cool $^{171}$Yb atoms to an average vibration number $\langle$nx$\rangle$ = 0.23(7) in the tightly binding direction, resulting in 93\% optical {$\pi$}pulse fidelity on the clock transition $^{1}S_{0} \rightarrow ^{3}P_{0}$. During cooling, the atoms selforganize into locations with maximal atomcavitycoupling, which will improve quantum metrology applications.

W. Xu, T. Šumarac, E.H. Qiu, M.L. Peters, Z. Li, S.H. Cantu, A. Menssen, M.D. Lukin, S. Colombo, and V. Vuletić, "BoseEinstein condensation by polarization gradient laser cooling", accepted into Phys. Rev. Lett. (5/2024); arXiv:2312.07708, DOI: 10.48550/arXiv.2312.07708
Attempts to create quantum degenerate gases without evaporative cooling have been pursued since the early days of laser cooling, with the consensus that polarization gradient cooling (PGC, also known as "optical molasses") alone cannot reach condensation. In the present work, we report that simple PGC can generate a small BoseEinstein condensate (BEC) inside a corrugated micrometersized optical dipole trap. The experimental parameters enabling BEC creation were found by machine learning, which increased the atom number by a factor of 5 and decreased the temperature by a factor of 2.5, corresponding to almost two orders of magnitude gain in phase space density. When the trapping light is slightly misaligned through a microscopic objective lens, a BEC of $\sim$250 $^{87}$Rb atoms is formed inside a local dimple within 40 ms of PGC.

D. Bluvstein, S.J. Evered, A.A. Geim, S.H. Li, H. Zhou, T. Manovitz, S. Ebadi, M. Cain, M. Kalinowski, D. Hangleiter, J.P. Bonilla Ataides, N. Maskara, I. Cong, X. Gao, P. Sales Rodriguez, T. Karolyshyn, G. Semeghini, M.J. Gullans, M. Greiner, V. Vuletić, and M.D. Lukin, "Logical quantum processor based on reconfigurable atom arrays", Nature 626, 58–65 (2024), DOI: 10.1038/s41586023069273
Suppressing errors is the central challenge for useful quantum computing1, requiring quantum error correction (QEC) for largescale processing. However, the overhead in the realization of errorcorrected ‘logical’ qubits, in which information is encoded across many physical qubits for redundancy, poses substantial challenges to largescale logical quantum computing. Here we report the realization of a programmable quantum processor based on encoded logical qubits operating with up to 280 physical qubits. Using logicallevel control and a zoned architecture in reconfigurable neutralatom arrays, our system combines high twoqubit gate fidelities, arbitrary connectivity, as well as fully programmable singlequbit rotations and midcircuit readout. Operating this logical processor with various types of encoding, we demonstrate improvement of a twoqubit logic gate by scaling surfacecode6 distance from d=3 to d=7, preparation of colourcode qubits with breakeven fidelities, faulttolerant creation of logical Greenberger–Horne–Zeilinger (GHZ) states and feedforward entanglement teleportation, as well as operation of 40 colourcode qubits. Finally, using 3D [8,3,2] code blocks, we realize computationally complex sampling circuits18 with up to 48 logical qubits entangled with hypercube connectivity with 228 logical twoqubit gates and 48 logical CCZ gates. We find that this logical encoding substantially improves algorithmic performance with error detection, outperforming physicalqubit fidelities at both crossentropy benchmarking and quantum simulations of fast scrambling. These results herald the advent of early errorcorrected quantum computation and chart a path towards largescale logical processors.

G. Panelli, S. C. Burd, E. J. Porter, and M. Kasevich, “DopplerFree ThreePhoton Spectroscopy on NarrowLine Optical Transitions,” arXiv:2403.09814, DOI: 10.48550/arXiv.2403.09814
We demonstrate coherent Dopplerfree threephoton excitation of the $^{1}S_{0}$ $\leftrightarrow$ $^{3}P_{0}$ optical clock transition and the $^{1}S_{0}$ $\leftrightarrow$ $^{3}P_{1}$ intercombination transition in freespace thermal clouds of $^{88}$Sr atoms. By appropriate orientation of the wavevectors of three lasers incident on the atoms, the firstorder Doppler shift can be eliminated for all velocity classes. Threephoton excitation of the $^{1}S_{0}$ $\leftrightarrow$ $^{3}P_{1}$ transition enables highcontrast Ramsey spectroscopy with interrogation times comparable to the 21$\mu$s natural lifetime using a single nearresonant laser source. Threephoton spectroscopy on the $^{1}S_{0}$ $\leftrightarrow$ $^{3}P_{0}$ clock transition, using only laser frequencies nearly resonant with the $^{1}S_{0}$ $\leftrightarrow$ $^{3}P_{0}$ and $^{1}S_{0}$ $\leftrightarrow$ $^{3}P_{1}$ transitions, enables a reduction in Doppler broadening by two orders of magnitude and a corresponding $\sim$ 470Hz linewidth without a confining potential.