1. 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.
  2. 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 Atom-Cavity Frequency Comparisons", Phys. Rev. Lett. 125, 201302 (2020), DOI 10.1103/PhysRevLett.125.201302
    We used three well-established quantum measurement techniques to set new limits on how strongly very low-mass candidates for hypothesized, but so far unobserved, "dark matter" interact with the atoms of regular matter familiar from the world around us. By using cross-comparisons 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.
  3. K. Matsuda, L. De Marco, J-R. 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. 1324-1327 (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 potassium-rubidium 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.
  4. 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 far-from-equilibrium dynamical regimes of a many-body spin-boson model with disordered couplings relevant for cavity QED and trapped ion experiments. Our study illustrated the resilience of glassy-like dynamics in the presence of active photonic degrees of freedom, suggesting that disordered quantum many-body systems with resonant photons or phonons can display a rich diagram of nonequilibrium responses, with near future applications for quantum information science.
  5. R. J. Lewis-Swan, D. Barberena, J. R. K. Cline, D. Young, J.K. Thompson, and A. M. Rey, "Cavity-QED 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 out-of-equilibrium phases exists in recent pump-probe 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 cavity-QED 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
  6. 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 ultra-cold 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 long-range 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
  7. M. Mamaev, I. Kimchi, R. Nandkishore, and A.M. Rey, "Tunable spin model generation in spin-orbital 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 spin-orbit-coupled laser driving. At half-filling, the resulting system can emulate a variety of iconic spin-1/2 models such as an Ising model, an XY model, a generic XXZ model with arbitrary anisotropy, or a collective one-axis 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 long-time dynamics. We explore these properties and discuss the role played by the system's symmetries. We also discuss experimentally viable implementations.
  8. 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 long-range XXZ spin models. We benchmark our simulator by probing a ferromagnetic to paramagnetic dynamical phase transition in the Lipkin-Meshkov-Glick 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 mean-field theoretical predictions. Our work introduces new possibilities in quantum simulation of anisotropic spin-spin interactions and quantum metrology enhanced by many-body entanglement.
  9. R. J. Lewis-Swan, S.R. Muleady, and A. M. Rey, "Detecting out-of-time-order 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 out-of-time-order correlations (OTOCs). Adopting the iconic Lipkin-Meshkov-Glick and transverse-field 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 quasi-adiabatic 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.
  10. M. H. Muñoz-Arias, P. Poggi, and I. Deutsch, “Nonlinear dynamics and quantum chaos of a family of kicked p-spin models”, Phys. Rev. E 103, 052212 (2021). DOI 10.1103/PhysRevE.103.052212 
    We introduce kicked p-spin models describing a family of transverse Ising-like models for an ensemble of spin-1/2 particles with all-to-all p-body interaction terms occurring periodically in time as delta-kicks. This is the natural generalization of the well-studied 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 out-of-time-order 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.
  11. 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 Lamb-Dicke confinement in magic-wavelength 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.
  12. R. Lewis-Swan, 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 mean-field 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.
  13. A. Cidrim, P. Orioli, C. Sanner, R. B. Hutson, J. Ye, R. Bachelard, and A. M. Rey, "Dipole-dipole frequency shifts in multilevel atoms", Phys. Rev. Lett 127, 013401 (2021), DOI 10.1103/PhysRevLett.127.013401 
    Dipole-dipole interactions lead to frequency shifts that are expected to limit the performance of next-generation 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 Clebsch-Gordan coefficients, we find that a simplified two-level 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 many-body physics.
  14. 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/s41586-022-04435-4
    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 state-of-the-art 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 low-depth, parametrized quantum circuits implementing optimal input states and measurement operators for a sensing task on a trapped-ion experiment. With 26 ions, we approach the fundamental sensing limit up to a factor of 1.45 $\pm$ 0.01, outperforming conventional spin-squeezing 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 entanglement-enabled protocols. We further perform on-device quantum-classical feedback optimization to ‘self-calibrate’ 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.
  15. 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.
  16. B. Li, J. Bartos, Y. Xie, and S-W Huang, "Time-magnified photon counting with 550-fs resolution", Optica 8, 1109 (2021) DOI 10.1364/OPTICA.420816
    The authors demonstrate a quantum temporal magnifier that enables femtosecond time-resolved photon counting with close-to-unity efficiency for the first time. The new technology can benefit many research fields such as fluorescence lifetime microscopy, time-of-flight imaging, light-in-flight imaging, time-gated Raman spectroscopy, and computational diffuse optical tomography.
  17. 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, co-trapped atomic species. Here, we outline an alternative approach that allows flexible encoding capabilities in single-species systems through the use of long-lived 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 large-scale systems that are already in operation.
  18. 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.
  19. 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 cavity-based 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 axion-sensitive cavity is coupled to an auxiliary resonant circuit through simultaneous two-mode 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 15-fold relative to the scan rate of a detector limited by vacuum noise.
  20. K. Gilmore, M. Affolter, R. J. Lewis-Swan, D. Barberena, E. Jordan, A. M. Rey, and J. J. Bollinger, "Quantum-enhanced sensing of displacements and electric fields with two-dimensional trapped-ion 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 many-body quantum-enhanced sensor to detect displacements and electric fields using a crystal of ~150 trapped ions. The center-of-mass vibrational mode of the crystal serves as a high-Q 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 many-body echo, a displacement is mapped into a spin rotation while avoiding quantum back-action 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.
  21. R. Kaubruegger, P. Silvi, C. Kokail, R. van Bijnen, A. M. Rey, J. Ye, A. M. Kaufman, and P. Zoller, "Variational spin-squeezing 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 spin-squeezed states on Sr atom tweezer arrays, where finite-range 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.
  22. M. A. Perlin, D. Barberena, M. Mamaev, B. Sundar, R. J. Lewis-Swan, and A. M. Rey, "Engineering infinite-range SU(n) interactions with spin-orbit-coupled 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 all-to-all SU(n)-symmetric couplings. Raman pulses that address internal spin states modify the atomic dispersion relation and induce spin-orbit coupling, which can act as a synthetic inhomogeneous magnetic field that competes with the SU(n) exchange interactions. We investigate the mean-field 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 intra-spin coherences. Our predictions are readily testable in current experiments with ultracold alkaline-earth(-like) atoms.
  23. 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 long-lived 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 many-body 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 excited-state decay rate, fully consistent with the theory prediction of an enhanced excited-state lifetime, on the ${^{1}S_{0}} - {^{3}P_{1}}$ transition in ${^{87}}$Sr atoms.
  24. 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 two-level 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.
  25. J. Huber, A. M. Rey, P. Rabi, "Realistic simulations of spin squeezing and cooperative coupling effects in large ensembles of interacting two-level 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 mean-field 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 mean-field 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 spin-squeezing effects or the dynamics and steady states of cavity QED models with ${10^5}$ interacting two-level systems. This opens up the possibility to perform accurate real-scale simulations of a diverse range of experiments in quantum optics or with solid-state spin ensembles under realistic laboratory conditions.
  26. 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 standing-wave cavity. By loading the atoms in partially delocalized Wannier-Stark 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 one-axis 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 short-range 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 lattice-based interferometers after accounting for primary sources of decoherence.
  27. C. Sanner, L. Sonderhouse, R. B. Hutson, L. Yan, W R. Milner, and J. Ye, "Pauli blocking of atom-light scattering", Science Vol 374, Issue 6570, pp. 979-983 (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.
  28. S. Omanakuttan, A. Mitra, M. J. Martin, and I. H. Deutsch, "Quantum optimal control of ten-level nuclear spin qudits in 87Sr", 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 radio-frequency magnetic field, the system is quantum controllable. Alkaline-earth-metal 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 light-shifting 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 Haar-random state in a time $T = \frac{4.5\pi}{\Omega_{rf}}$ with average fidelity $$ = 0.9992, and an arbitrary Haar-random SU(10) map in a time $T = \frac{24\pi}{\Omega_{rf}}$ with average fidelity $$ = 0.9923.
  29. S. B. Jäger, H. Liu, J. Cooper, M. J. Holland, "Collective emission of an atomic beam into an off-resonant 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 atom-cavity 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.
  30. L-Y Chih, M. J. Holland, "Reinforcement-learning-based matter-wave interferometer in a shaken optical lattice”, Physical Review Research 3, 033279 (2021), DOI: 10.1103/PhysRevResearch.3.033279
    We demonstrate the design of a matter-wave 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 lattice-based 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.
  31. 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 steady-state 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 free-space spontaneous emission and T2 dephasing processes.
  32. A. Shankar, J. T. Reilly, S. B. Jäger, and M. J. Holland, "Subradiant-to-Subradiant 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 steady-state superradiance in a bad cavity laser is preceded by a dissipative phase transition between two distinct phases of steady-state 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.
  33. S. B. Jäger, H. Liu, A. Shankar, J. Cooper, M. J. Holland, "Regular and bistable steady-state 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 pre-excited 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 transit-time 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 steady-state 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 free-space 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.
  34. H. Liu, S. B. Jäger, X. Yu, S. Touzard, A. Shankar, M. J. Holland, T. L. Nicholson, "Rugged mhz-linewidth 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 sought-after applications of ultracoherent lasers in challenging environments.
  35. W.G. Tobias, K. Matsuda, J-R. Li, C. Miller, A. N. Carroll, T. Bilitewski, A. M. Rey, J. Ye, "Reactions between layer-resolved molecules mediated by dipolar spin exchange", Science, 375, p1299-1303 (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 layer-resolved state preparation and imaging of ultracold potassium-rubidium molecules confined to two-dimensional planes in an optical lattice. The rotational coherence was maximized by rotating the electric field relative to the light polarization for state-insensitive 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 two-dimensional systems.
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  37. T-W 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 high-numerical-aperture optical tweezers using the trapped atoms and compare with numerical computations of the metasurface-lens 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 neutral-atom arrays.
  38. M. O. Brown, S. R. Muleady, W. J. Dworschack, R. J. Lewis-Swan, A. M. Rey, O. Romero-Isart, and C. A. Regal, "Time-of-Flight Quantum Tomography of Single Atom Motion", Nat. Phys. (2023), DOI: 10.1038/s41567-022-01890-8
    A single particle trapped in a harmonic potential can exhibit rich motional quantum states within its high-dimensional 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 solid-state 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 time-of-flight measurements, which, combined with trap harmonic evolution, grants us access to all quadrature distributions. Starting with non-classical motional states of a trapped neutral atom, we demonstrate the Wigner function negativity and coherence of non-stationary 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.
  39. 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. Johnston-Halperin, R. Joynt, E. Kapit, J. Klein-Seetharaman, 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 1-23  (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 quantum-aware and quantum-proficient 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 quantum-aware engineers, design of a first quantum engineering course, accessible to all STEM students, is described; 2) for the education and training of quantum-proficient 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 hands-on 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 solid-state technologies, nanofabrication, and control and readout electronics.
  40. A. Derevianko, K. Gibble, L. Hollberg, N. R. Newbury, C. Oates, M. S. Safronova, L. C. Sinclair, N. Yu, "Fundamental Physics with a State-of-the-Art Optical Clock in Space", Quantum Sci. Technol. 7, 044002 (2022), DOI: 10.1088/2058-9565/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 state-of-the-art 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.
  41. Y-D. Tsai, J. Eby, M. S. Safronova, "Direct detection of ultralight dark matter bound to the Sun with space quantum sensors", Nat Astron (2022), DOI: 10.1038/s41550-022-01833-6
    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 two-clock 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 bound-state halo in our solar system. We present sensitivity projections for space-based 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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  43. Z. Lasner, A. Lunstad, C. Zhang, L. Cheng, J. M. Doyle, "Vibronic branching ratios for nearly-closed 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 laser-cooling scheme, including magneto-optical trapping and sub-Doppler 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.
  44. A. Aeppli, A. Chu, T. Bothwell, C. J. Kennedy, D. Kedar, P. He, A. M. Rey, and J. Ye, "Hamiltonian engineering of spin-orbit coupled fermions in a Wannier-Stark 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 many-body systems. An optical lattice clock based on partially delocalized Wannier-Stark states in a gravity-tilted shallow lattice supports superior quantum coherence and adjustable interactions via spin-orbit coupling, thus presenting a powerful spin model realization. The relative strength of the on-site and off-site 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 off-site Wannier-Stark transitions, realizing a ferromagnetic to paramagnetic dynamical phase transition.
  45. B. Sundar, D. Barberena, A. Piñeiro Orioli, A. Chu, J. K. Thompson, A. M. Rey, and R. J. Lewis-Swan, "Bosonic pair production and squeezing for optical phase measurements in long-lived 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 long-lived 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 two-mode 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 quantum-enhanced 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 next-generation optical atomic clocks.
  46. C. Overstreet, P. Asenbaum, J. Curti, M. Kim, and M. A. Kasevich, “Observation of a Gravitational Aharonov-Bohm Effect.” Science 375, no. 6577 (January 14, 2022): 226–29, DOI: 10.1126/science.abl7152
    The Aharonov-Bohm 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 Aharonov-Bohm effect. 
  47. B. K. Malia, Y. Wu, J. Martínez-Rincón, M. A. Kasevich, "Distributed quantum sensing with a mode-entangled network of spin-squeezed atomic states", Nature 612, 661–665 (2022), DOI: 10.1038/s41586-022-05363-z
    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.
  48. 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/s41567-022-01794-7
    Comparisons of high-accuracy 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 zero-dead-time Yb optical lattice clock with an Al+ single-ion 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.
  49. D. R. Leibrandt, S. G. Porsev, C. Cheung, M. S. Safronova, "Prospects of a thousand-ion Sn2+ Coulomb-crystal clock with sub-10^(−19) inaccuracy", (May, 2022), DOI: 10.48550/arXiv.2205.15484
    We propose a many-ion optical atomic clock based on three-dimensional 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 three-dimensional ion crystals cancel each other, and a laser-accessible 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$^{2+}$ Coulomb-crystal clocks.
  50. E. D. Caldwell, L. C. Sinclair, N. R. Newbury, and J-D Deschenes, "The Time Programmable Frequency Comb: Generation and Application to Quantum-Limited Dual-Comb Ranging", Nature 610, 667–673 (2022), DOI: 10.1038/s41586-022-05225-8
    The classic self-referenced 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 quantum-limited 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 quantum-limited sensitivity in sensing applications since the programmable comb can be configured to coherently track weak returning pulse trains at the shot-noise limit. To highlight its capabilities, we use this programmable comb in a ranging system, reducing the detection threshold by ~5,000-fold to enable nearly quantum-limited 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, comb-based spectroscopy, pump-probe experiments, and compressive sensing should benefit from coherent control of the comb-pulse time and phase.
  51. X. Zhang, K. Beloy, Y. S. Hassan, W. F. McGrew, C-C Chen, J. L. Siegel, T. Grogan, A. D. Ludlow, "Sub-recoil clock-transition 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, two-stage Doppler cooling is typically used to bring atoms to the uK regime. Here, we implement a pulsed radial cooling scheme using the ultranarrow 1S0-3P0 clock transition in ytterbium to realize sub-recoil temperatures, down to tens of nK. Together with sideband cooling along the one-dimensional 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 10-19 level.
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  53. N. Hoghooghi, S. Xing, P. Chang, D. Lesko, A. Lind, G. Rieker, S. Diddams, "1-GHz mid-infrared frequency comb spanning 3 to 13 μm", Light Sci Appl 11, 264 (2022), DOI: 10.1038/s41377-022-00947-w
    Mid-infrared (MIR) spectrometers are invaluable tools for molecular fingerprinting and hyper-spectral imaging. Among the available spectroscopic approaches, GHz MIR dual-comb absorption spectrometers have the potential to simultaneously combine the high-speed, 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 mode-locked laser, robust all-fiber Er amplifiers and intra-pulse difference frequency generation (IP-DFG) of few-cycle 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 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 non-repetitive events that are currently inaccessible with other sources.
  54. A. Mitra, S. Omanakuttan, M. J. Martin, G. W. Biedermann, I. H. Deutsch, "Practical and fundamental limits of neutral atom entanglement using Rydberg dressing", arXiv:2205.12866, DOI: 10.48550/arXiv.2205.12866
    We revisit the implementation of a two-qubit entangling gate, the Mølmer-Sørensen gate, using the adiabatic Rydberg dressing paradigm. We study the implementation of rapid adiabatic passage using a two-photon transition, which does not require the use of an ultra-violet laser, and can be implemented using only amplitude modulation of one field with all laser frequencies fixed. We find that entangling gate fidelities, comparable to the one-photon excitation, are achievable with the two-photon excitation. Moreover, we address how the adiabatic dressing protocol can be used to implement entangling gates outside the regime of a perfect Rydberg blockade. We show that using adiabatic dressing we can achieve a scaling of gate fidelity set by the fundamental limits to entanglement generated by the Rydberg interactions while simultaneously retaining limited population in the doubly excited Rydberg state. This allows for fast high fidelity gates for atoms separated beyond the blockade radius.
  55. 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 intermediate-scale quantum (NISQ) devices pose engineering challenges to realizing quantum machine learning (QML) advantages. Recently, a series of QML computational models inspired by the noise-tolerant 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 well-known model for neural circuits in the brain. Our quantum RNN (qRNN) makes use of the natural Hamiltonian dynamics of an ensemble of interacting spin-1/2 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 long-term memory by taking advantage of several key features of this platform such as interatomic species interactions, and quantum many-body scars.
  56. S. Ostermann, V. Walther, and S. F. Yelin, "Superglass formation in an atomic BEC with competing long-range 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 many-body system with two competing and substantially different long-range interaction potentials where the dynamical instability towards density order can give way to a disordered amorphous solid, which exhibits local density modulations but no long-range periodic order. We consider a two-dimensional Bose-Einstein condensate in the Rydberg-dressing 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 soft-core interactions arising due to Rydberg dressing and infinite-range 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.
  57. 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 Goemans-Williamson algorithm, which is a useful approximation for various NP-hard problems, such as MaxCut. Our method exceeds the performance of analogous classical methods on a diverse subset of well-studied MaxCut problems from the GSet library.
  58. J. Z. Lu, R. A. Bravo, K. Hou, G. A. Dagnew, S. F. Yelin, K. Najafi, "Learning quantum symmetries with interactive quantum-classical variational algorithms", arXiv:2206.11970, https://doi.org/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 black-box 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 quantum-classical 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 re-learning 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 non-local 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.
  59. B. Wu, G. P. Greve, C. Luo, J. K. Thompson, “Site-dependent selection of atoms for homogeneous atom-cavity coupling,” arXiv:2104.01201 submitted to PRA, DOI: 10.48550/arXiv.2104.01201
    We demonstrate a method to obtain homogeneous atom-cavity coupling by selecting and keeping 87Rb atoms that are near maximally coupled to the cavity's standing-wave 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 atom-cavity coupling will potentially enhance entanglement generation, intracavity driving of atomic transitions, cavity-optomechanics, and quantum simulations. This approach can easily be extended to other atomic species with microwave or optical transitions.
  60. G P. Greve, C. Luo, B. Wu, J. K. Thompson, “Entanglement-Enhanced Matter-Wave Interferometry in a High-Finesse Cavity”, arXiv:2110.14027, DOI: 
    Entanglement is a fundamental resource that allows quantum sensors to surpass the standard quantum limit set by the quantum collapse of independent atoms. Collective cavity-QED systems have succeeded in generating large amounts of directly observed entanglement involving the internal degrees of freedom of laser-cooled atomic ensembles. Here we demonstrate cavity-QED entanglement of external degrees of freedom to realize a matter-wave 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 non-demolition measurements and cavity-mediated 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 Mach-Zehnder light-pulse 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 mean-field quantum many-body physics.
  61. 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 non-equilibrium phases of matter supported by photon-mediated 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 non-equilibrium 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.
  62. 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 light-matter 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.
  63. 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 atom-light 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 state-of-the-art momentum separation in excess of 400 $\hbar k$. This technique can be applied to any two-level system at arbitrary coupling strength, with broad application in coherent quantum control.
  64. S. Buckley-Bonanno, S. Ostermann, O. Rubies-Bigorda, T. L. Patti, S. F. Yelin, "Optimized geometries for cooperative photon storage in an impurity coupled to a two-dimensional atomic array", Phys. Rev. A 106, 053706 (2022), DOI: 10.1103/PhysRevA.106.053706
    The collective modes of two-dimensional 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 non-centered 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.
  65. W. Zhong, X. Gao, S. F. Yelin, K. Najafi, "Many-body localized hidden Born machine", arXiv:2207.02346, 10.48550/arXiv.2207.02346
    Born Machines are quantum-inspired generative models that leverage the probabilistic nature of quantum states. Here, we present a new architecture called many-body 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 many-body states, and non-local 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 many-body systems as learning resources, and reveal a powerful connection between disorder, interaction, and learning in quantum systems. 
  66. J. T. Reilly, S. B. Jäger, J. Cooper, M. J. Holland, "Adiabatic Control of Decoherence-Free-Subspaces 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 decoherence-free 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 multi-particle 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 so-called 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.
  67. 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 Schrieffer-Wolff transformation which allows to eliminate the bosonic degrees of freedom after self-consistently 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 mean-field approximation.
  68. J. D. Wilson, S. B. Jäger, J. T. Reilly, A. Shankar, M.L. Chiofalo, M. J. Holland, "Beyond one-axis twisting: Simultaneous spin-momentum 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 one-axis twisting (OAT), where a many-particle entangled state of one degree of freedom is generated by a non-linear 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) one-axis 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 multi-parameter or auxiliary measurement schemes than those prepared by standard spin squeezing.
  69. G. W. Harmon, J. T. Reilly, M. J. Holland, S. B. Jäger, "Mean-field Floquet theory for a three-level cold-atom 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 V-level system allows for an efficient closed lasing cycle to be sustained on a dipole-forbidden transition without the need for incoherent repumping. This is made possible by utilizing an additional dipole-allowed 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 mean-field 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 mean-field results to a second-order cumulant approach. The work provides simple methods for understanding complex physics that occur in cold atom lasers with narrow line transitions.
  70. N. Schine, A. W. Young, W. Eckner, M. Martin, A. M. Kaufman, "Long-Lived Bell states in an array of optical clock qubits", Nature Physics volume 18, pages 1067–1073 (2022), DOI: 10.1038/s41567-022-01678-w
    The generation of long-lived 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 Rydberg-based 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 single-qubit gates on the optical clock transition and two-qubit 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 many-qubit gates and cluster state generation, as well as explorations of the transverse field Ising model and Hubbard models with entangled or finite-range-interacting tunnellers.
  71. S. Colombo, E. Pedrozo-Penafiel, A. Adiyatullin, Z. Li, E. Mendez, C. Shu, and V. Vuletić, "Time-reversal-based quantum metrology with many-body entangled states", Nature Phys. (2022); DOI: 10.1038/s41567-022-01653-5
    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 many-body states with non-Gaussian probability distributions. Here, by implementing an effective time-reversal protocol in an optically engineered many-body spin Hamiltonian, we demonstrate a quantum measurement with non-Gaussian states with performance beyond the limit of the readout scheme. This signal amplification through a time-reversed 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 time-reversal-based 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 optical-transition atomic clocks.
  72. N. Irtija, J. Plusquellic, E. E. Tsiropoulou, J. Goldberg, D. Lobser, and D. Stick, "Design and analysis of digital communication within an SoC-based control system for trapped-ion quantum computing", IEEE Transactions on Quantum Engineering, vol. 4, pp. 1-24, 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, real-time feedback, and latency requirements vary widely depending on the qubit type. In this paper, we evaluate the performance of modern System-on-Chip (SoC) architectures in meeting the control demands associated with performing quantum gates on trapped-ion qubits, particularly focusing on communication within the SoC. A principal focus of this paper is the data transfer latency and throughput of several high-speed on-chip mechanisms on Xilinx multi-processor 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. Worst-case and average-case bandwidth requirements for a custom gate sequencer core are compared with the experimental results. The lowest-variability, highest-throughput data-transfer mechanism is DMA between the real-time 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 trapped-ion control systems, the gate abstraction scheme and measured communication rates are applicable to a broad range of quantum computing technologies.
  73. M. Nie, B. Li, K. Jia, Y. Xie, J. Yan, S.-N. Zhu, Z. Xie, and S.-W. Huang, "Dissipative soliton generation and real-time dynamics in microresonator-filtered fiber lasers", Light Sci Appl 11, 296 (2022), DOI: 10.1038/s41377-022-00998-z
    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 self-starting, 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 microresonator-filtered fiber laser in both theory and experiment. We bring theoretical insight into the mode-locking principle, discuss the parameters effect on soliton properties, and provide experimental guidelines for broadband soliton generation. We predict chirped bright dissipative soliton with flat-top 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 ultrahigh-speed time magnifier, we study the real-time soliton formation and interaction dynamics and experimentally observe soliton Newton’s cradle. Our study will benefit the design of the novel, high-efficiency and self-starting microcombs for real-world applications.
  74. 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: 10.1088/1361-6404/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 think-aloud 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.
  75. 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/s41586-022-05479-2
    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 potassium-rubidium molecules confined to two-dimensional planes, where the spin-1/2 is encoded in the molecular rotational levels. The dipolar interaction gives rise to a shift of the rotational transition frequency and a collision-limited 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 many-body spin dynamics and spin-motion physics utilizing the strong, tunable dipolar interaction.
  76. C. Kiehl, D. Wagner, T-W. 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 spin-exchange coherence for hyperfine transitions that takes into account a nonstatic population distribution. In this regime, Rabi oscillations exhibit nontrivial time-domain signals that allow verification of vapor-cell parameters. We find excellent agreement between theory and experiment, which will aid in benchmarking sensitivities of Rabi measurement applications.
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  78. A. M. Polloreno, J. L. Beckey, J. Levin, A. Shlosberg, J. K. Thompson, M. Foss-Feig, 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 two-level 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.
  79. A. Chu, A. P. Orioli, D. Barberena, J. K. Thompson, A. M. Rey, "Photon-mediated 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 cavity-mediated 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 single-particle and collective shifts of the ground state levels. We discuss the rich many-body dynamics that can be realized in the synthetic ladder including pair production processes, chiral transport and light-cone correlation spreading. The latter illustrates that an effective notion of locality can be engineered in a system with fully collective interactions.
  80. 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 Lamb-Dicke 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 high-precision optical frequency references outside of low vibration laboratory environments.
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  82. 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 trapped-ion 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 Lamb-Dicke 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 ground-state qubits in commonly used trapped-ion 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.
  83. J.M. Robinson, M. Miklos, Y.M. Tso, C.J. Kennedy, T. Bothwell, D. Kedar, J.K. Thompson, J. Ye, "Direct comparison of two spin squeezed optical clocks below the quantum projection noise limit", arXiv:2211.08621, DOI: 10.48550/arXiv.2211.08621
    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 state-of-the-art 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 strong-coupling cavity QED for quantum non-demolition (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 sub-ensembles, 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.
  84. 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/s41586-023-06360-6
    Neutral-atom arrays trapped in optical potentials are a powerful platform for studying quantum physics, combining precise single-particle control and detection with a range of tunable entangling interactions. For example, these capabilities have been leveraged for state-of-the-art frequency metrology as well as microscopic studies of entangled many-particle 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 Rydberg-mediated squeezing with a neutral-atom 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 one-second 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 half-hour 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 spin-squeezing protocol in a programmable atom-array clock opens the door to a wide range of quantum-information inspired techniques for optimal phase estimation and Heisenberg-limited optical atomic clocks.
  85. 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 cavity-based axion-dark-matter 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 factor-of-5.6 acceleration relative to a quantum limited search for the same tone. This speed-up is achieved by dynamically coupling the resonator mode to a second (readout) mode with balanced swapping and two-mode squeezing interactions, which results in both visibility-bandwidth and peak-visibility increase. A small fractional imbalance between the two interaction rates yields further scan-rate enhancement and we demonstrate that an eightfold acceleration can be achieved.
  86. 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 low-loss couplers", arXiv:2304.06162, DOI: https://doi.org/10.48550/arXiv.2304.06162
    We design and test a low-loss interface between superconducting 3-dimensional microwave cavities and 2-dimensional 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 self-Kerr nonlinearity to the cavity, remaining linear in high photon number operations.
  87. M. H. Muñoz-Arias, I. H. Deutsch, and P. M. Poggi, "Phase-Space Geometry and Optimal State Preparation in Quantum Metrology with Collective Spins", PRX QUANTUM 4, 020314 (2023), DOI: 10.1103/PRXQuantum.4.020314
    We revisit well-known 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 two-axis countertwisting and twisting-and-turning Hamiltonians, where we provide analytical expressions for all the relevant optimal timescales. Finally, we propose a generalization of these models to include p-body collective interaction (or p-order twisting), beyond the usual case of p = 2. Using our geometric framework, we prove a no-go theorem for the local optimality of these models for p > 2.
  88. M. H. Muñoz-Arias, K. Chinni, and Pablo M. Poggi (Deutsch group), "Floquet time crystals in driven spin systems with all-to-all p-body 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 p-spin models, which describe a collection of spin-1/2 particles with all-to-all p-body interactions. Given the mean-field 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 time-crystalline 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 four-body interactions (p = 4) gives rise to both a usual period-doubling crystal and also a period-quadrupling phase. We develop a comprehensive framework to predict robust subharmonic response in classical area-preserving maps, and use this as a basis to predict the occurrence and characterize the stability of the resulting mean-field FTC phases in the quantum regime. Our analysis reveals that the robustness of the time-crystal 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.
  89. T-H 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/s41566-023-01364-0

    The introduction of nonlinear nanophotonic devices to the field of optical frequency comb metrology has enabled new opportunities for low-power and chip-integrated clocks, high-precision frequency synthesis, and broad bandwidth spectroscopy. However, most of these advances remain constrained to the near-infrared 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 multi-segment nanophotonic thin-film lithium niobate (LN) waveguides that combine engineered dispersion and chirped quasi-phase 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 gap-free frequency comb coverage spanning 330 to 2400 nm. The conversion efficiency from the near-infrared pump to the UV-Visible region of 350-550 nm is nearly 20\%. Harmonic generation via the $\chi^{(2)}$ nonlinearity in the same waveguide directly yields the carrier-envelope 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.
  90. H. Liu, G. M. Brodnik, J. Zang, D. R. Carlson, J. A. Black, S. B. Papp, "Threshold and laser-conversion in nanostructured-resonator parametric oscillators", arXiv:2305.16449, DOI: 10.48550/arXiv.2305.16449

    We explore optical parametric oscillation (OPO) in nanophotonic resonators, enabling arbitrary, nonlinear phase-matching and nearly lossless control of energy conversion. Such pristine OPO laser converters are determined by nonlinear light-matter interactions, making them both technologically flexible and broadly reconfigurable. We utilize a nanostructured inner-wall modulation in the resonator to achieve universal phase-matching for OPO-laser conversion, but coherent backscattering also induces a counterpropagating pump laser. This depletes the intra-resonator optical power in either direction, increasing the OPO threshold power and limiting laser-conversion 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 nanostructured-resonator OPO laser-conversion circuits, fully integrated on chip and unlimited by group-velocity dispersion. Our work demonstrates the fundamental connection between OPO laser-conversion efficiency and the resonator coupling rate, subject to the relative phase and power of counterpropagating pump fields. We achieve (40$\pm$4) mW of on-chip power, corresponding to (41$\pm$4)\% conversion efficiency, and discover a path toward near-unity OPO laser conversion efficiency.
  91. J-R 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 three-dimensional molecular quantum gas", Nature Physics 17, 1144–1148 (2021), DOI: 10.1038/s41567-021-01329-6

    Ultracold polar molecules possess long-range, 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 two-body loss over elastic interactions, which prevents efficient evaporative cooling. Although recent work has demonstrated controlled interactions by confining molecules to a two-dimensional geometry, a general approach for tuning molecular interactions in a three-dimensional 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 field-induced 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 long-lived bulk quantum gas system with tunable long-range interactions, paving the way for the study of collective quantum many-body physics.
  92. L. R. Liu, P. B. Changala, M. L. Weichman, Q. Liang, J. Toscano, J. Klos, S. Kotochigova, D. J. Nesbitt, and J. Ye, “Collision-induced C60 rovibration relaxation probed by state-resolved nonlinear spectroscopy”, Phys. Rev. X Quantum 3, 030332 (2022), DOI: 10.1103/prxquantum.3.030332

    Quantum state-resolved 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 many-atom system. Here we combine state-specific optical pumping, buffer gas collisions, and ultrasensitive intracavity nonlinear spectroscopy to initiate and probe the rotation-vibration 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.
  93. 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 Wannier-Stark 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 $3.5 \times 10^{-19}$.
  94. D. González-Cuadra, 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: 10.48550/arXiv.2303.06985

    Simulating the properties of many-body fermionic systems is an outstanding computational challenge relevant to material science, quantum chemistry, and particle physics. Although qubit-based quantum computers can potentially tackle this problem more efficiently than classical devices, encoding non-local fermionic statistics introduces an overhead in the required resources, limiting their applicability on near-term architectures. In this work, we present a fermionic quantum processor, where fermionic models are locally encoded in a fermionic register and simulated in a hardware-efficient manner using fermionic gates. We consider in particular fermionic atoms in programmable tweezer arrays and develop different protocols to implement non-local tunneling gates, guaranteeing Fermi statistics at the hardware level. We use this gate set, together with Rydberg-mediated 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 fermion-qubit 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.
  95. R. Hutson, W. R. Milner, L. Yan, C. Sanner, and J. Ye, “Observation of mHz-level cooperative Lamb shifts in an optical atomic clock”, Science, submitted (2023), DOI: 10.48550/arXiv.2303.05613

    We report on the direct observation of resonant electric dipole-dipole interactions in a cubic array of atoms in the many-excitation limit. The interactions, mediated by single-atom couplings to the shared electromagnetic vacuum, are shown to produce spatially-dependent cooperative Lamb shifts when spectroscopically interrogating the mHz-wide optical clock transition in strontium-87. We show that the ensemble-averaged shifts can be suppressed below the level of evaluated systematic uncertainties for state-of-the-art 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 non-resonant 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 many-body physics of spins with long-range interactions mediated by propagating photons.
  96. 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 ultra-sensitive broadband laser spectroscopy detects SARS-CoV-2 infection”, J. Breath Res. 17, 036001 (2023), DOI: 10.1088/1752-7163/acc6e4

    Rapid testing is essential to fighting pandemics such as coronavirus disease 2019 (COVID-19), the disease caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Exhaled human breath contains multiple volatile molecules providing powerful potential for non-invasive diagnosis of diverse medical conditions. We investigated breath detection of SARS-CoV-2 infection using cavity-enhanced direct frequency comb spectroscopy (CE-DFCS), a state-of-the-art laser spectroscopic technique capable of a real-time massive collection of broadband molecular absorption features at ro-vibrational quantum state resolution and at parts-per-trillion volume detection sensitivity. Using a total of 170 individual breath samples (83 positive and 87 negative with SARS-CoV-2 based on reverse transcription polymerase chain reaction tests), we report excellent discrimination capability for SARS-CoV-2 infection with an area under the receiver-operating-characteristics curve of 0.849(4). Our results support the development of CE-DFCS as an alternative, rapid, non-invasive test for COVID-19 and highlight its remarkable potential for optical diagnoses of diverse biological conditions and disease states.
  97. 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. 778-783 (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 non-equilibrium 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 ro-vibrational 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 non-ergodic 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.
  98. 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 563-568 (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 research-based knowledge of student learning of quantum mechanics, we present a study on the use of Quantum Composer, a flexible, flow-based 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 think-aloud interviews where students worked through an exercise exploring the statics and time-dynamics of quantum states in single and double harmonic well potentials. Student Outcomes are then cross-coded 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.
  99. 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: 10.1088/2058-9565/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 post-secondary 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.
  100. V. Borish, A. Werth, and H. J. Lewandowski, "Seeing quantum mechanics: The role of quantum experiments", 2022 PERC Proceedings (Grand Rapids, MI, July 13-14, 2022), edited by B. W. Frank, D. L. Jones, and Q. X. Ryan, DOI: https://doi.org/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.
  101. 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 “single-photon 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 single-photon experiments in undergraduate courses, asking how and why they use the experiments. We describe the most commonly used experiments in both quantum and beyond-first-year 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.
  102. H. Zhang, A. Chu, C. Luo, J. K. Thompson, A. M. Rey, "Control and amplification of Bloch oscillations via photon-mediated interactions", arXiv:2301.08296 (2023), DOI: 10.48550/arXiv.2301.08296

    We propose a scheme to control and enhance atomic Bloch oscillations via photon-mediated interactions in an optical lattice supported by a standing-wave cavity with incommensurate lattice and cavity wavelengths. Our scheme uses position-dependent atom-light 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 position-dependent atom-cavity couplings to perform non-destructive measurements of single-particle Bloch oscillations, and to generate long-range interactions self-tuned 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 state-of-the-art cavity QED experiments for the exploration of many-body dynamics in self-tunable potentials.
  103. D. Barberena, R. J. Lewis-Swan, A. M. Rey, and J. K. Thompson, "Ultra Narrow Linewidth Frequency Reference via Measurement and Feedback", Comptes Rendus. Physique, Online first (2023), pp. 1-14, DOI: https://doi.org/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 atom-cavity system. We calculate these effects to obtain fundamental limits for frequency estimation and stabilization across a range of values of input light intensities and atom-light interaction strengths, estimate these limits in state-of-the-art cavity experiments with alkaline-earth atoms and identify favorable operating conditions. We find that the achievable linewidths are comparable to those of the superradiant laser.
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  105. D. J. Young, A. Chu, E. Y. Song, D. Barberena, D. Wellnitz, Z. Niu, V. M. Schäfer, R. J. Lewis-Swan, A. M. Rey, and J. K. Thompson, "Observing Dynamical Phases of a Bardeen-Cooper-Schrieffer Superconductor in a Cavity QED Simulator", arXiv:2306.00066 (2023), DOI: 10.48550/arXiv.2306.00066

    In conventional Bardeen-Cooper-Schrieffer (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 out-of-equilibrium 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 long-lived electronic transition in $^{88}Sr$ atoms coupled to an optical cavity and represents interactions between electrons as photon-mediated interactions through the cavity. To fully explore the phase diagram, we manipulate the ratio between the single-particle dispersion and the interactions after a quench and perform real-time tracking of subsequent dynamics of the superconducting order parameter using non-destructive measurements. We observe regimes where the order parameter decays to zero ("phase I"), assumes a non-equilibrium steady-state value ("phase II"), or exhibits persistent oscillations ("phase III") in the form of a self-generated 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 mean-field effects like the spectral form factor, and for increasing coherence time for quantum sensing.
  106. 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 n-level spin-orbit coupled alkaline-earth fermionic atoms with SU(n) symmetric interactions. We consider three-dimensional lattices with tunneling along one dimension, and the internal levels treated as a synthetic dimension, realizing an n-leg 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 long-time 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.
  107. 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

    Two-dimensional 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 solid-state systems as well as in ultracold quantum gases. Here, we propose to leverage the tremendous control offered by rotating two-dimensional trapped-ion crystals in a Penning trap to simulate the dynamical phases of two-dimensional p+ip superfluids. This is accomplished by mapping the presence or absence of a Cooper pair into an effective spin-1/2 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 mean-field corrections. More broadly, our work opens the door to use trapped-ion systems to explore exotic models of topological superconductivity and also paves the way to generate and manipulate skyrmionic spin textures in these platforms.
  108. J. T. Young, S. R. Muleady, M. A. Perlin, A. M. Kaufman, and A. M. Rey, "Enhancing spin squeezing using soft-core 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 short-range, soft-core potential with an external drive, we can transform naturally emerging Ising interactions into an XX spin model while opening a many-body 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 soft-core interactions can generate spin squeezing comparable to an all-to-all Ising model even in the presence of relevant decoherence, the same amount of squeezing as the decoherence-free XX spin model with $1/{r^{3}}$ dipolar interactions, and a 5.8 dB gain over the decoherence-free XX spin model with $1/{r^{6}}$ interactions.
  109. T. Bilitewski, G. Domínguez-Castro, D. Wellnitz, A. M. Rey, and L. Santos, "Momentum-selective pair creation of spin excitations in dipolar bilayers", arXiv:2302.09059 Submitted (2023), DOI: https://doi.org/10.48550/arXiv.2302.09059

    We study the temporal growth and spatial propagation of quantum correlations in a two-dimensional bilayer realising a spin-1/2 quantum XXZ model with couplings mediated by long-range 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 momentum-dependent 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 state-of-the-art experiments with Rydberg atoms, magnetic atoms, and polar molecule arrays.
  110. 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 long-lived entangled spin-squeezed states within a manifold of many-body 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 single-particle rotations to a dark state where squeezing can be stored. Our findings, readily testable in current optical cavity experiments with alkaline-earth-like atoms, can open a path for dissipative generation and storage of metrologically useful states in optical transitions.
  111. J. Franke, S. R. Muleady, R. Kaubruegger, F. Kranzl, R. Blatt, A. M. Rey, M. Joshi, and C. Roos, "Quantum-enhanced sensing on an optical transition via emergent collective quantum correlations", arXiv:2303.10688 Submitted (2023), DOI: https://doi.org/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 state-dependent interactions that decay as a power-law function of the ion separation. We show our sensor can be made to behave as a one-axis-twisting (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 spin-wave 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 non-Gaussian states in the form of atomic multi-headed cat states in the Q-distribution. 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 Ramsey-type interferometer, where we reduce the measurement uncertainty by $-3.2\pm0.5$ dB below the standard quantum limit for N = 51 ions.
  112. S. R. Muleady, M. Yang, S. R. White, and A. M. Rey, "Validating phase-space methods with tensor networks in two-dimensional spin models with power-law interactions", arXiv:2305.17242 Submitted (2023), DOI: https://doi.org/10.48550/arXiv.2305.17242

    Using a recently developed extension of the time-dependent variational principle for matrix product states, we evaluate the dynamics of 2D power-law interacting XXZ models, implementable in a variety of state-of-the-art experimental platforms. We compute the spin squeezing as a measure of correlations in the system, and compare to semiclassical phase-space 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 resource-intensive tensor network representation of the dynamics. We also compare the steady-state behavior of DTWA to thermal ensemble calculations with tensor networks. Our results open a way to benchmark dynamical calculations for two-dimensional quantum systems, and allow us to rigorously validate recent predictions for the generation of scalable entangled resources for metrology in these systems.
  113. M. Mamaev, D. Barberena, and A. M. Rey, "Spin squeezing in mixed-dimensional anisotropic lattice models", arXiv:2306.05313 Submitted (2023), DOI: https://doi.org/10.48550/arXiv.2306.05313

    We describe a theoretical scheme for generating scalable spin squeezing with nearest-neighbour interactions between spin-1/2 particles in a 3D lattice, which are naturally present in state-of-the-art 3D optical lattice clocks. We propose to use strong isotropic Heisenberg interactions within individual planes of the lattice, forcing the constituent spin-1/2s 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 spin-orbit 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.
  114. 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, “Integrated-Photonics-Based Architectures for Polarization-Gradient 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 trapped-ion cooling schemes, polarization-gradient and electromagnetically-induced-transparency cooling, for $^{88}Sr^{+}$ ions using a visible-wavelength integrated-photonics platform and present the design of the key integrated devices.
  115. T. Sneh, A. Hattori, M. Notaros, S. Corsetti, and J. Notaros (Chiaverini group), “Design of Integrated Visible-Light Polarization Rotators and Splitters”, Frontiers in Optics (FiO) 2022, paper JTu5A.48 (2022) DOI: https://doi.org/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 off-axis polarization rotator, and a mode-coupling polarization splitter are designed in a silicon-nitride platform.
  116. 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: https://doi.org/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.
  117. N. Schine, A. W. Young, W. J. Eckner, M. J. Martin & A. M. Kaufman, "Long-lived Bell states in an array of optical clock qubits", Nat. Phys. 18, 1067–1073 (2022), DOI: 10.1038/s41567-022-01678-w

    The generation of long-lived entanglement in optical atomic clocks is one of the main goals of quantum metrology. Arrays of neutral atoms, where Rydberg-based 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 three-dimensional optical lattice to prepare an ensemble of strontium-atom pairs in their motional ground state. We engineer global single-qubit gates on the optical clock transition and two-qubit entangling gates via adiabatic Rydberg dressing, enabling the generation of Bell states with a state-preparation-and-measurement-corrected fidelity of 92.8(2.0)\% (87.1(1.6)\% without state-preparation-and-measurement 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 long-lived Bell states can be useful for enhancing metrological stability and bandwidth. In the future, atomic rearrangement will enable the implementation of many-qubit gates and cluster state generation, as well as explorations of the transverse field Ising model.
  118. S. Omanakuttan, A. Mitra, M. J. Martin, I. H. Deutsch, “Qudit entanglers using quantum optimal control”, PRX Quantum 4, 040333 (2023), DOI: https://doi.org/10.1103/PRXQuantum.4.040333

    We study the generation of two-qudit entangling quantum logic gates using two techniques in quantum optimal control. We take advantage of both continuous, Lie-algebraic control and digital, Lie-group control. In both cases, the key is access to a time-dependent Hamiltonian which can generate an arbitrary unitary matrix in the group SU($d^{2}$). We find efficient protocols for creating high-fidelity 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 well-known 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 spin-resonance, a tensor AC-Stark shift, and Rydberg dressing, which allows us to generate an arbitrary symmetric entangling two-qudit 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.
  119. 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 mode-locked lasers, photonic frequency microcombs based on dissipative Kerr and quadratic cavity solitons in high-Q 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.
  120. M. Nie, K. Jia, Y. Xie, S. Zhu, Z. Xie, and S.-W. Huang, "Synthesized spatiotemporal mode-locking and photonic flywheel in multimode mesoresonators", Nature Commun. 13, 6395 (2022), DOI: https://doi.org/10.1038/s41467-022-34103-0

    Dissipative Kerr soliton (DKS) frequency combs—also known as microcombs—have arguably created a new field in cavity nonlinear photonics, with a strong cross-fertilization between theoretical, experimental, and technological research. Spatiotemporal mode-locking (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 ultrahigh-quality-factor Fabry–Pérot (FP) mesoresonator based on graded index multimode fiber (GRIN-MMF). Complementing the two-step 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 state-of-the-art. Our results show the potential of GRIN-MMF FP mesoresonators as an ideal testbed for high-dimensional nonlinear cavity dynamics and photonic flywheel with ultrahigh coherence and ultralow timing jitter.
  121. [Temporary Placeholder only]

  122. 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.
  123. 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 high-accuracy optical clocks and could enable Heisenberg-limited QLS.
  124. A. Young, W. Eckner, N. Schine, A. M. Childs, A. Kaufman, "Tweezer-programmable quantum walks in a Hubbard-regime lattice", Science 377, 6608 pp 885-889 (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 continuous-time quantum walks of single atoms on a square lattice and perform proof-of-principle 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.
  125. J.Y. Lee, J. Ramette, M.A. Metlitski, V. Vuletić, W.W. Ho, and S. Choi, "Landau-Forbidden Quantum Criticality in Rydberg Quantum Simulators", submitted to Phys. Rev. Lett., Phys. Rev. Lett. 131, 083601 (2023), DOI: 10.1103/PhysRevLett.131.083601

    The Landau-Ginzburg-Wilson 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 one-dimensional array of individually trapped neutral atoms interacting strongly via Rydberg states, and demonstrate through extensive numerical simulations that it hosts a variety of symmetry-breaking 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.
  126. Y.-T. Chen, M. Szurak, Y.-C. Yeh, B. Hu, J. de Hond, B. Braverman, and V. Vuletić, "High finesse bow-tie cavity for strong atom-photon coupling in Rydberg arrays", Opt. Express 30(21), 37426-37435 (2022), 10.1364/OE.469644

    We report a high-finesse bow-tie 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 in-vacuum aspheric lenses with a numerical aperture (NA) of 0.35 and is capable of housing NA = 0.5 microscope objectives. In addition, the large atom-mirror 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.
  127. P.L. Ocola, I. Dimitrova, B. Grinkemeyer, E. Guardado-Sanchez, T. Djordjević, P. Samutpraphoot, V. Vuletić, and M.D. Lukin, "Control and Entanglement of Rydberg-Atom Qubits Near a Nanoscale Device", submitted to Phys. Rev. Lett., arXiv:2210.12879, DOI: 10.48550/arXiv.2210.12879

    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 two-atom entanglement can be generated and maintained at distances of 100 microns from a nanoscale dielectric device. Using coherent manipulation of individual qubits and entanglement-assisted sensing, we map the spatio-temporal properties of the electric field environment, enabling its control and the integration of Rydberg arrays with micro- and nanoscale devices.
  128. S. Colombo, E. Pedrozo-Penafiel, and V. Vuletić, "Entanglement-Enhanced 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 many-body 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 many-body entangled states to operate quantum sensors beyond the SQL. In particular, we focus on the potential of applying quantum entanglement to state-of-the-art optical atomic clocks. In addition, we present recently developed time-reversal protocols that make use of complex states with high quantum Fisher information without requiring sub-SQL measurement resolution. We discuss the prospects for reaching near-Heisenberg limited quantum metrology based on such protocols.
  129. Z. Vendeiro, J. Ramette, A. Rudelis, M. Chong, J. Sinclair, L. Stewart, A. Urvoy, and V. Vuletić, "Machine-learning-accelerated Bose-Einstein 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 Bose-Einstein 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 room-temperature 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 machine-learning approach.
  130. J. Ramette, J. Sinclair, N.P. Breuckmann, and V. Vuletić, "Fault-Tolerant 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 fault-tolerant 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 sub-threshold behavior, reaching threshold with ∼1% bulk errors and ∼10% interface errors. This implies that fault-tolerant scaling of error-corrected modular devices is within reach using existing technology.
  131. 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.", submitted to Phys. Rev. Lett.; arXiv:2306.03190, DOI: 10.48550/arXiv.2306.03190

    Considering the unique energy level structure of the one-axis 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 many-atom 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.
  132. Z. Li, S. Colombo, C. Shu, G. Velez, S. Pilatowsky Cameo, R. Schmied, S. Choi, M.D. Lukin, E. Pedrozo-Peñafiel, and V. Vuletić, "Improving Metrology with Quantum Scrambling", Science Vol 380, Issue 6652 pp. 1381-1384, 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 entanglement-enhanced metrology. A time-reversal protocol is used to observe a simultaneous exponential growth of both the metrological gain and the out-of-time-order 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.
  133. 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 two-level atoms driven by multiple time-dependent 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 556-nm magneto-optical trap (MOT) with a slowing force of ≈ $60F_{rad}$. We show that a square-wave 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%.
  134. 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 Earth-orbiting 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 https://doi.org/10.1088/2058-9565/ac9f2b

    We present a concept for a high-precision optical atomic clock (OAC) operating on an Earth-orbiting space station. This pathfinder science mission will compare the space-based OAC with one or more ultra-stable terrestrial OACs to search for space-time-dependent signatures of dark scalar fields that manifest as anomalies in the relative frequencies of station-based and ground-based clocks. This opens the possibility of probing models of new physics that are inaccessible to purely ground-based 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 space-based OACs.
  135. 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. 871-879 (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 guided-mode sources, allowing the generation and full control of free-space radiation directly from within a single 150 nm layer Ta2O5, showing low loss across visible and near-infrared spectra. We generate diverging circularly-polarized beams at the challenging 461 nm wavelength that can be directly used for magneto-optical traps of strontium atoms, constituting a fundamental building block for a range of atomic-physics-based quantum technologies. Our generated topological vortex beams and spatially-varying polarization emitters could open unexplored light-matter interaction pathways, enabling a broad new photonic-atomic paradigm. Our platform highlights the generalizability of nanoscale devices for visible-laser emission and will be critical for scaling quantum technologies.
  136. 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 phase-matching 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 four-wave 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 group-velocity 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.
  137. 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 multi-beam generation and atomic clock packaging on chip", Light Sci. Appl. 12, 83 (2023), DOI: 10.1038/s41377-023-01081-x

    The commercialization of atomic technologies requires replacing laboratory-scale laser setups with compact and manufacturable optical platforms. Complex arrangements of free-space beams can be generated on chip through a combination of integrated photonics and metasurface optics. In this work, we combine these two technologies using flip-chip bonding and demonstrate an integrated optical architecture for realizing a compact strontium atomic clock. Our planar design includes twelve beams in two co-aligned magneto-optical 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 co-propagating beams at lattice and clock wavelengths. These beams emit collinearly and vertically to probe the center of the magneto-optical 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.
  138. R. Bustos-Ramirez, 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 Electro-Optically Modulated Kerr Soliton to a Chip-Scale Mode-Locked Laser PIC via Regenerative Harmonic Injection Locking", J. Light. Technol. 40, 1742–1748 (2022), DOI: 10.1109/JLT.2021.3135235

    An InP-based mode-locked laser photonic integrated circuit with a repetition rate of 10 GHz is optically synchronized to a SiN microresonator-based dissipative Kerr soliton with a rep- etition rate of 305 GHz. The synchronization is achieved through regenerative harmonic injection locking assisted with electro-optic division which results in an optical frequency division factor of 18. The repetition rate of the dissipative Kerr soliton is stabilized through electro-optic division and transferred to the mode-locked 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 mode-locked laser’s repetition rate beat as a feedback point.
  139. J. A. Black, G. Brodnik, H. Liu, S.-P. Yu, D. R. Carlson, J. Zang, T. C. Briles, and S. B. Papp, "Optical-parametric oscillation in photonic-crystal ring resonators", Optica 9, 1183–1189 (2022), DOI: 10.1364/OPTICA.469210

    By-design access to laser wavelength, especially with integrated photonics, is critical to advance quantum sensors, such as optical clocks and quantum-information systems, and open opportunities in optical communication. Semiconductor-laser 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 laser-wavelength access by versatile customization of optical-parametric oscillation (OPO) with a photonic-crystal ring resonator (PhCR). Leveraging the exquisite control of laser propagation provided by a photonic crystal in a traveling-wave ring resonator, we enable OPO generation across a wavelength range of 1234–2093 nm with a 1550-nm pump and 1016–1110 nm with a 1064-nm pump. Moreover, our platform offers pump-to-sideband conversion efficiency of >10% and negligible additive optical-frequency 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.
  140. 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 ultra-high 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, low-cost solutions for applications including quantum information sciences, precision navigation and timing, metrology, and high-capacity 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 CMOS-compatible 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 cavity-intrinsic 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 ring-resonators that reduce the high-frequency noise by the nonlinear Brillouin process and the low-frequency noise by Pound–Drever–Hall locking to the ultra-low 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.
  141. A. Quinn, J. Metzner, J. Muldoon, I. Moore, S. Brudney, S. Das, D. Allcock, Y. Joglekar, "Observing super-quantum correlations across the exceptional point in a single, two-level trapped ion", arXiv:2304.12413, DOI: 10.48550/arXiv.2304.12413

    Quantum theory provides rules governing much of the microscopic world, and among its counter-intuitive consequences are correlations that exceed the bounds from local, classical theories. In two-level quantum systems - qubits - unitary dynamics theoretically limit these spatiotemporal quantum correlations, called Bell/Clauser-Horn-Shimony-Holt or Leggett-Garg inequalities, to $2 \sqrt{2}$ or 1.5 respectively. Experiments with state-of-the-art qubits have approached the spatial, Bell and temporal, Leggett-Garg quantum correlation bounds. Here, using a dissipative, trapped $^{40}Ca^{+}$ ion governed by a two-level, non-Hermitian Hamiltonian, we observe temporal correlation values up to 1.703(4) for the Leggett-Garg parameter $K_3$, clearly exceeding the hitherto inviolable Lüder's bound of 1.5. These excesses occur across the exceptional point of the parity-time symmetric Hamiltonian responsible for the qubit's non-unitary, coherent dynamics. Distinct evolution speeds for antipodal qubit states, which violate the unified (Mendelstam-Tamm or Margolus-Levitin) bound $\tau_{τQSL}$ for the transit time based on quantum speed limit, result in the super-quantum $K_3$ values observed over a wide parameter range. Our results demonstrate that post-selected, coherent dynamics of non-Hermitian Hamiltonians pave the way for enhanced quantum correlations that exceed protocols based on unitary or dissipative dynamics.
  142. 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

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

  144. O. Rubies-Bigorda, 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 many-body 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 two-dimensional geometries. In addition, we study the robustness of superradiance in the case of non-unit filling and position disorder.
  145. O. Rubies-Bigorda, 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 finite-sized ordered arrays of dipole-dipole coupled quantum emitters, based on incoherent driving of the atomic ensemble. In particular, we show that a maximal coupling to long-lived 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.
  146. H. Ma, O. Rubies-Bigorda, S. Yelin, "Superradiance and subradiance in a gas of two-level atoms", arXiv:2205.15255, DOI: arxiv.org/abs/2205.15255

    Cooperative effects describe atomic ensembles with exchange of photonic excitations, such as dipole-dipole 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 many-body systems. This method, which allows to study extended systems with arbitrarily large number of particles can be formulated by an effective, nonlinear, two-atom master equation that describes the dynamics using a closed form which treats single- and many-body terms on an equal footing. We apply this method to a homogeneous gas of initially inverted two-level atoms, and demonstrate the appearance of both superradiance and subradiance, identifying a many-body coherence term as the source of these cooperative effects. We describe the many-body 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 time-dependence of subradiance, and the phase change of the radiated field during the cooperative decay.
  147. 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 long-standing open question. Both, energy levels and decay rates, are modified by the exchange of real and virtual photons making up the dipole-dipole interaction. We introduce a method to theoretically study weakly-driven, low-excited ensembles of two-level atoms and obtain an analytic description of the collective Lamb shift and collective decay rate via a self-consistent 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.
  148. F. Shah, T. Patti, O. Rubies-Bigorda, S. Yelin, "Quantum computing with subwavelength atomic arrays", Phys. Rev. A 109, 012613 (2024), DOI: 10.1103/PhysRevA.109.012613

    Photon-mediated interactions in subwavelength atomic arrays have numerous applications in quantum science. In this manuscript, we explore the potential of three-level quantum emitters, or ``impurities" embedded in a two-dimensional atomic array to serve as a platform for quantum computation. By exploiting the altered behavior of impurities as a result of the induced dipole-dipole interactions mediated by subwavelength array, we implement a set of universal quantum gates consisting of the $\sqrt{iSWAP}$ and single-qubit 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 two-qubit Bell states, as well as the entangled three-qubit GHZ state. These findings establish subwavelength emitter arrays as an alternative platform for quantum computation and quantum simulation.
  149. 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 single-qubit 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.
  150. 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 uniform-field regime. In non-relativistic 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.
  151. 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 operator-valued measure in this situation.
  152. 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 second-order processes of the system, inducing the requisite two-phonon 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 single-photon, strong-coupling 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 near-term experimental systems.
  153. A. Kyle, C. Rau, W. Warfield, A. Kwiatkowski, J. Teufel, K. Lehnert, T. Dennis, [Combes Group]  "Optically Distributing Remote Two-node Microwave Entanglement using Doubly Parametric Quantum Transducers", arXiv:2211.09762, DOI: 10.48550/arXiv.2211.09762

    Doubly-parametric quantum transducers (DPTs), such as electro-opto-mechanical 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 two-mode 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 microwave-microwave 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 down-conversion of each half of an optical two-mode squeezed vacuum state is the most robust topology. Finally, we numerically evaluate the amount of microwave--microwave 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.
  154. M. Nicotra, J. Shao, J. Combes, A. Theurkauf, P. Axelrad, L-Y 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 Example-driven 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.
  155. C. Luo, H. Zhang, V. P. W. Koh, J. D. Wilson, A. Chu, M. J. Holland, A. M. Rey, J. K. Thompson, "Cavity-Mediated Collective Momentum-Exchange Interactions", arXiv:2304.01411, DOI: 10.48550/arXiv.2304.01411

    Quantum simulation and sensing hold great promise for providing new insights into nature, from understanding complex interacting systems to searching for undiscovered physics. Large ensembles of laser-cooled atoms interacting via infinite-range photon mediated interactions are a powerful platform for both endeavours. Here, we realize for the first time momentum-exchange interactions in which atoms exchange their momentum states via collective emission and absorption of photons from a common cavity mode. The momentum-exchange interaction leads to an observed all-to-all Ising-like interaction in a matter-wave interferometer, which is useful for entanglement generation. A many-body energy gap also emerges, effectively binding interferometer matter-wave packets together to suppress Doppler dephasing, akin to Mössbauer spectroscopy. The tunable momentum-exchange interaction provides a new capability for quantum interaction-enhanced matter-wave interferometry and for realizing exotic behaviors including simulations of superconductors and dynamical gauge fields.
  156. C. LeDesma, K. Mehling, J. Shao, J. D. Wilson, P. Axelrad, M. M. Nicotra, M. J. Holland, D. Z. Anderson, "A Machine-Designed 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 free-space 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 time-space 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 state-of-the art inertial and gravitational sensors that will have a wide range of potential applications.
  157. J. T. Reilly, J. D. Wilson, S. B. Jäger, C. Wilson, M. J. Holland, "Optimal Generators for Quantum Sensing", arXiv:2305.15556, DOI: 10.48550/arXiv.2305.15556

    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.
  158. N. Hoghooghi, S. Xing, P. Chang, D. Lesko, A. Lind, G. Rieker, S. Diddams, “Broadband 1-GHz Mid-infrared Frequency Comb,” Light: Science & Applications 11, 1-7, (2022), DOI: 10.1038/s41377-022-00947-w

    Mid-infrared (MIR) spectrometers are invaluable tools for molecular fingerprinting and hyper-spectral imaging. Among the available spectroscopic approaches, GHz MIR dual-comb absorption spectrometers have the potential to simultaneously combine the high-speed, 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 $\mu µm$ mode-locked laser, robust all-fiber Er amplifiers and intra-pulse difference frequency generation (IP-DFG) of few-cycle 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 non-repetitive events that are currently inaccessible with other sources.

Strongly Related Publications by Q-SEnSE Investigators

  1. R. Srinivas, S. C. Burd, H. M. Knaack, R. T. Sutherland, A. Kwiatkowski, S. Glancy, E. Knill, D. J. Wineland, D. Leibfried, A. C. Wilson, D. T. C. Allcock, D. H. Slichter, "High-fidelity laser-free universal control of two trapped ion qubits", Nature 597, 209 (2021), DOI https://doi.org/10.1038/s41586-021-03809-4
  2. A. W. Young, W. J. Eckner, W. R. Milner, D. Kedar, M. A. Norcia , E. Oelker , N. Schine , J. Ye & A. M. Kaufman, "Half-minute-scale atomic coherence and high relative stability in a tweezer clock", Nature, Vol 588, 17 December 2020
  3. E. Pedrozo-Peñafiel, S. Colombo, C. Shu, A. F. Adiyatullin, Z. Li, E. Mendez, B.s Braverman, A. Kawasaki, D. Akamatsu, Y. Xiao and V. Vuletić, "Entanglement on an optical atomic-clock transition", Nature 588, 414–418, 16 December 2020, https://doi.org/10.1038/s41586-020-3006-1
  4. J. Ye, N. Mavalvala, R. G. Beausoleil, P. M. Dehmer, L. L. Dimauro, M. Gaarde, S. Girvin, C. H. Greene, T. J. Ha, M. Kasevich, M. Lipson, M. D. Lukin, A. M. Lyyra, P. J. Reynolds, M. Safronova, and P. Zoller, "Manipulating Quantum Systems: An Assessment of Atomic, Molecular, and Optical Physics in the United States", http://nasedu/AMO2020 (2019) (2019). 10.17226/25613
  5. S. C. Burd, R. Srinivas, J. J. Bollinger, A. C. Wilson, D. J. Wineland, D. Leibfried, D. H. Slichter, and D. T. C. Allcock, "Quantum amplification of mechanical oscillator motion", Science 364, 1163-1165 (2019). 10.1126/science.aaw2884
  6. K. C. McCormick, J. Keller, S. C. Burd, D. J. Wineland, A. C. Wilson, and D. Leibfried, "Quantum-enhanced sensing of a single-ion mechanical oscillator", Nature 572, 86-90 (2019). 10.1038/s41586-019-1421-y
  7. K. van Bibber, K. Lehnert, and A. Chou, "Putting the squeeze on axions", Phys Today 72, 48 (2019). 10.1063/PT.3.4227
  8. J. Rudolph, T. Wilkason, M. Nantel, H. Swan, C. M. Holland, Y. Jiang, B. E. Garber, S. P. Carman, and J. M. Hogan, "Large Momentum Transfer Clock Atom Interferometry on the 689 nm Intercombination Line of Strontium", arXiv:191005459 (2019).
  9. M. Mamaev, R. Blatt, J. Ye, and A. M. Rey, "Cluster State Generation with Spin-Orbit Coupled Fermionic Atoms in Optical Lattices", Phys Rev Lett 122, 160402 (2019). 10.1103/PhysRevLett.122.160402
  10. J. M. Robinson, E. Oelker, W. R. Milner, W. Zhang, T. Legero, D. G. Matei, F. Riehle, U. Sterr, and J. Ye, "Crystalline optical cavity at 4 K with thermal-noise-limited instability and ultralow drift", Optica 6, 240-243 (2019). 10.1364/optica.6.000240
  11. M. A. Norcia, A. W. Young, W. J. Eckner, E. Oelker, J. Ye, and A. M. Kaufman, "Seconds-scale coherence in a tweezer-array optical clock", Science 366, 93-97 (2019). 10.1126/science.aay0644
  12. E. Oelker, R. B. Hutson, C. J. Kennedy, L. Sonderhouse, T. Bothwell, A. Goban, D. Kedar, C. Sanner, J. M. Robinson, G. E. Marti, D. G. Matei, T. Legero, M. Giunta, R. Holzwarth, F. Riehle, U. Sterr, and J. Ye, "Demonstration of 4.8 × 10−17 stability at 1 s for two independent optical clocks", Nat Photonics 13, 714-719 (2019). 10.1038/s41566-019-0493-4
  13. D. Barberena, R. J. Lewis-Swan, J. K. Thompson, and A. M. Rey, "Driven-dissipative quantum dynamics in ultra-long-lived dipoles in an optical cavity", Phys Rev A 99, 053411 (2019). 10.1103/PhysRevA.99.053411
  14. L. Anderegg, L. W. Cheuk, Y. Bao, S. Burchesky, W. Ketterle, K.-K. Ni, and J. M. Doyle, "An Optical Tweezer Array of Ultracold Molecules", Science 365, 1156-1158 (2019). 10.1126/science.aax1265
  15. A. D. Draper, R. K. Cole, A. S. Makowiecki, J. Mohr, A. Zdanowicz, A. Marchese, N. Hoghooghi, and G. B. Rieker, "Broadband dual-frequency comb spectroscopy in a rapid compression machine", Opt Express 27, 10814-10825 (2019). 10.1364/oe.27.010814
  16. C. B. Alden, S. C. Coburn, R. J. Wright, E. Baumann, K. Cossel, E. Perez, E. Hoenig, K. Prasad, I. Coddington, and G. B. Rieker, "Single-Blind Quantification of Natural Gas Leaks from 1 km Distance Using Frequency Combs", Envir Sci Tech Lib 53, 2908-2917 (2019). 10.1021/acs.est.8b06259
  17. L. Ríos, B. Pollard, D. R. Dounas-Frazer, and H. J. Lewandowski, "Using think-aloud interviews to characterize model-based reasoning in electronics for a laboratory course assessment", Phys Rev Phys Educ Res 15, 010140 (2019). 10.1103/PhysRevPhysEducRes.15.010140
  18. M. Malnou, D. A. Palken, B. M. Brubaker, L. R. Vale, G. C. Hilton, and K. W. Lehnert, "Squeezed Vacuum Used to Accelerate the Search for a Weak Classical Signal", Phys Rev X 9, 021023 (2019). 10.1103/PhysRevX.9.021023
  19. S. M. Brewer, J.-S. Chen, A. M. Hankin, E. R. Clements, C. W. Chou, D. J. Wineland, D. B. Hume, and D. R. Leibrandt, "An 27 Al + quantum-logic clock with systematic uncertainty below 10−18", Phys Rev Lett 123, 033201 (2019). 10.1103/PhysRevLett.123.033201
  20. H. Bergeron, L. C. Sinclair, W. C. Swann, I. Khader, K. C. Cossel, M. Cermak, J. D. Deschenes, and N. R. Newbury, "Femtosecond time synchronization of optical clocks off of a flying quadcopter", Nat Commun 10, 7 (2019). 10.1038/s41467-019-09768-9
  21. L. C. Sinclair, H. Bergeron, W. C. Swann, I. Khader, K. C. Cossel, M. Cermak, N. R. Newbury, and J. D. Deschenes, "Femtosecond optical two-way time-frequency transfer in the presence of motion", Phys Rev A 99, 023844 (2019). 10.1103/PhysRevA.99.023844
  22. A. Shankar, L. Salvi, M. L. Chiofalo, N. Poli, and M. J. Holland, "Squeezed state metrology with Bragg interferometers operating in a cavity", Quantum Science and Technology 4, 045010 (2019). 10.1088/2058-9565/ab455d
  23. A. Shankar, G. P. Greve, B. Wu, J. K. Thompson, and M. Holland, "Continuous Real-Time Tracking of a Quantum Phase Below the Standard Quantum Limit", Phys Rev Lett 122, 233602 (2019). 10.1103/PhysRevLett.122.233602
  24. W. R. Milner, J. M. Robinson, C. J. Kennedy, T. Bothwell, D. Kedar, D. G. Matei, T. Legero, U. Sterr, F. Riehle, H. Leopardi, T. M. Fortier, J. A. Sherman, J. Levine, J. Yao, J. Ye, and E. Oelker, "Demonstration of a Timescale Based on a Stable Optical Carrier", Phys Rev Lett 123, 173201 (2019). 10.1103/PhysRevLett.123.173201
  25. R. B. Hutson, A. Goban, G. E. Marti, L. Sonderhouse, C. Sanner, and J. Ye, "Engineering Quantum States of Matter for Atomic Clocks in Shallow Optical Lattices", Phys Rev Lett 123, 123401 (2019). 10.1103/PhysRevLett.123.123401
  26. P. He, M. A. Perlin, S. R. Muleady, R. J. Lewis-Swan, R. B. Hutson, J. Ye, and A. M. Rey, "Engineering spin squeezing in a 3D optical lattice with interacting spin-orbit-coupled fermions", Physical Review Research 1, 033075 (2019). 10.1103/PhysRevResearch.1.033075
  27. A. Piñeiro Orioli and A. M. Rey, "Dark states of multilevel fermionic atoms in doubly-filled optical lattices", Phys Rev Lett 123, 223601 (2019). 10.1103/PhysRevLett.123.223601
  28. C. Qu and A. M. Rey, "Spin squeezing and many-body dipolar dynamics in optical lattice clocks", Phys Rev A 100, 041602 (2019). 10.1103/PhysRevA.100.041602
  29. M. S. Safronova, D. Budker, D. DeMille, D. F. J. Kimball, A. Derevianko, and C. W. Clark, "Search for new physics with atoms and molecules", Rev Mod Phys 90, 025008 (2018). 10.1103/RevModPhys.90.025008
  30. M. A. Norcia, A. W. Young, and A. M. Kaufman, "Microscopic Control and Detection of Ultracold Strontium in Optical-Tweezer Arrays", Phys Rev X 8, 041054 (2018). 10.1103/PhysRevX.8.041054
  31. A. Goban, R. B. Hutson, G. E. Marti, S. L. Campbell, M. A. Perlin, P. S. Julienne, J. P. D’Incao, A. M. Rey, and J. Ye, "Emergence of multi-body interactions in a fermionic lattice clock", Nature 563, 369-373 (2018). 10.1038/s41586-018-0661-6
  32. I. Kozyryev, Z. Lasner, and J. M. Doyle, "Enhanced Sensitivity to Ultralight Bosonic Dark Matter in the Spectra of the Linear Radical SrOH", arXiv:180508185 (2018).
  33. I. Kozyryev, L. Baum, L. Aldridge, P. Yu, E. E. Eyler, and J. M. Doyle, "Coherent Bichromatic Force Deflection of Molecules", Phys Rev Lett 120, 063205 (2018). 10.1103/PhysRevLett.120.063205
  34. T. Thiele, Y. Lin, M. O. Brown, and C. A. Regal, "Self-Calibrating Vector Atomic Magnetometry through Microwave Polarization Reconstruction", Phys Rev Lett 121, 153202 (2018). 10.1103/PhysRevLett.121.153202
  35. C. A. Weidner and D. Z. Anderson, "Simplified landscapes for optimization of shaken lattice interferometry", New J Phys 20, 075007 (2018). 10.1088/1367-2630/aad36c
  36. C. A. Weidner and D. Z. Anderson, "Experimental Demonstration of Shaken-Lattice Interferometry", Phys Rev Lett 120, 263201 (2018). 10.1103/PhysRevLett.120.263201
  37. M. A. Norcia, J. R. K. Cline, J. A. Muniz, J. M. Robinson, R. B. Hutson, A. Goban, G. E. Marti, J. Ye, and J. K. Thompson, "Frequency Measurements of Superradiance from the Strontium Clock Transition", Phys Rev X 8, 021036 (2018). 10.1103/PhysRevX.8.021036
  38. P. Wcisło, P. Ablewski, K. Beloy, S. Bilicki, M. Bober, R. Brown, R. Fasano, R. Ciuryło, H. Hachisu, T. Ido, J. Lodewyck, A. Ludlow, W. McGrew, P. Morzyński, D. Nicolodi, M. Schioppo, M. Sekido, R. Le Targat, P. Wolf, X. Zhang, B. Zjawin, and M. Zawada, "New bounds on dark matter coupling from a global network of optical atomic clocks", Science Advances 4, eaau4869 (2018). 10.1126/sciadv.aau4869
  39. M. A. Norcia, R. J. Lewis-Swan, J. R. K. Cline, B. Zhu, A. M. Rey, and J. K. Thompson, "Cavity-mediated collective spin-exchange interactions in a strontium superradiant laser", Science 361, 259-262 (2018). 10.1126/science.aar3102
  40. J. P. Bartolotta, M. A. Norcia, J. R. K. Cline, J. K. Thompson, and M. J. Holland, "Laser cooling by sawtooth-wave adiabatic passage", Phys Rev A 98, 023404 (2018). 10.1103/PhysRevA.98.023404
  41. M. A. Norcia, J. R. K. Cline, J. P. Bartolotta, M. J. Holland, and J. K. Thompson, "Narrow-line laser cooling by adiabatic transfer", New J Phys 20, 023021 (2018). 10.1088/1367-2630/aaa950
  42. Q.-Y. Liang, A. V. Venkatramani, S. H. Cantu, T. L. Nicholson, M. J. Gullans, A. V. Gorshkov, J. D. Thompson, C. Chin, M. D. Lukin, and V. Vuletić, "Observation of three-photon bound states in a quantum nonlinear medium", Science 359, 783-786 (2018). 10.1126/science.aao7293
  43. D. S. Wild, E. Shahmoon, S. F. Yelin, and M. D. Lukin, "Quantum Nonlinear Optics in Atomically Thin Materials", Phys Rev Lett 121, 123606 (2018). 10.1103/PhysRevLett.121.123606
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