Spring 2025 Colloquium Schedule

Spring 2025 Colloquium YouTube Channel

Colloquia are Wednesdays at 4:00 p.m. in the JILA Auditorium. 

Coffee, tea and cookies will be available in G1B31 (across from G1B20) from 3:30 - 3:50 p.m.

January 15 — "Toward Quantum Imaging of Nuclei"

  • Presenter: Miguel Arratia, University of California, Riverside
  • Host: Jamie Nagle
  • Abstract: The atomic nucleus emerges from interacting quantum particles called quarks and gluons, but how this happens remains unknown. This might be elucidated with quantum-level "images" of their position, orbital motion, spin alignment, and entanglement. I will describe recent and upcoming experiments at the Thomas Jefferson Laboratory that use a high-intensity, high-energy electron beam to probe a wide range of nuclear targets, from polarized lithium to lead. I will also explain how these studies pave the way for future research at the Electron-Ion Collider (EIC), which will usher in a new era by providing a novel tool: particle jets. To advance EIC jet physics, we are developing next-generation, highly granular calorimeter systems, which can be enhanced with state-of-the-art AI/ML methodologies. I will summarize recent prototype testing conducted at various facilities and discuss plans for further testing and construction in the near future.

January 22 — "Economic inequality from a statistical physics point of view"

  • Presenter: Victor Yakovenko, Physics and JQI, University of Maryland, College Park
  • Host: Rahul Nandkishore
  • Abstract: Inequality is an important and seemingly inevitable aspect of the human society. Various manifestations of inequality can be derived from the concept of entropy in statistical physics. In a stylized model of monetary economy, the probability distribution of money among the agents converges to the exponential Boltzmann-Gibbs law due to entropy maximization. Our analysis of empirical data shows that income distributions in the USA and other countries exhibit a two-class structure. The lower class (about 97% of population) is characterized by the "thermal" exponential distribution, whereas the upper class (about 3%) by the "superthermal" Pareto power law. The total income share of the upper class expands and contracts dramatically during booms and busts in financial markets. We also found that global inequality in energy consumption and CO2 emissions has been decreasing since 1980 (likely due to the globalization) and converging toward the exponential distribution. The decrease in global inequality stopped recently, when maximal entropy was reached, as we predicted in advance. All papers are available at http://physics.umd.edu/~yakovenk/econophysics/

January 29 — "A world from a sheet of paper"

  • Presenter: Tadashi Tokieda, Stanford University
  • Host: Leo Radzihovsky

  • Abstract: Starting from just a sheet of paper, by folding, stacking, crumpling, sometimes tearing, we will explore a diversity of phenomena, from magic tricks and geometry to elasticity and the traditional Japanese art of origami. Much of the lecture consists of table-top demonstrations, which you can try later with friends and family.

    So, take a sheet of paper . . .

  • Bio: Tadashi Tokieda is a professor at Stanford University. He grew up as a painter in Japan, became a classical philologist (not to be confused with philosopher) in France and, having earned a PhD in pure mathematics from Princeton, has been an applied mathematician in England and the US. He is also active in outreach in the developing world, especially via the African Institute for Mathematical Sciences (AIMS) as well as the YouTube channel Numberphile. Tokieda was invited to deliver a public lecture at the 2018 ICM and at the 2022 ICM.

**Special Colloquium** Monday, February 3 — "A view into the flow and fracture of glacier ice"

  • Presenter: Joanna Millstein, Colorado School of Mines
  • Time: 11:00 a.m.
  • Location: JILA Auditorium
  • Host: Mike Ritzwoller
  • Abstract: Glaciers deform through the driving force of their own weight and display dramatic responses to both external forcing, such as changes in climate, and internal forcing like variations in stress. Determining the response of glaciers and ice sheets to such forcing was, until very recently, limited by sparse observations and data across the cryosphere. The rapid expansion of pertinent and available satellite-based data has created an opportunity to understand the processes contributing to dynamic change through melting and calving, the fracture of icebergs. I leverage the expanding volume of satellite observations to develop and refine models of ice flow and ice fracture through mechanical and statistical frameworks. In this talk, I will discuss a modern reexamination of the constitutive law for glacier ice and new parameterizations for large ice fractures. These observational studies improve higher-order ice sheet models, enabling a more complete view of ice sheet change. This research showcases the power of quantifying and calibrating the processes of ice flow and ice fracture to understand ice sheet stability and to assess future projections of glaciers and ice sheets in a changing climate.

February 5 — "Tabletop X-Ray Lasers: From Star Wars to Quantum Sculpting"

  • Presenter: Margaret Murnane, JILA, University of Colorado, Boulder
  • Host: Tobin Munsat
  • Abstract: Ever since the invention of the laser over 60 years ago, scientists have been striving to create x-ray lasers. In the same way that visible lasers can concentrate light energy far better than a light bulb, a directed beam of x-rays would have many useful applications. The problem was that until recently, ridiculously high powers were needed to make an x-ray laser. Some of the first x-ray lasers were powered by nuclear detonations as as part of the “star wars” program in the 1980s. To make a practical, tabletop-scale, x-ray laser source required taking a very different approach. The story behind how this happened is surprising, where we learned how to transform ultrafast laser light into directed beams of x-rays by sculpting the wave function of a radiating electron. Along the way, we also learned to generate the shortest strobe light in existence, and to build near-perfect short wavelength microscopes.

**Canceled** February 12 — "Quantum Simulation and Sensing with Atoms Interacting via Photons"

  • Presenter: James K. Thompson, JILA, NIST, University of Colorado, Boulder
  • Host: Ana Maria Rey
  • Abstract: Photons bouncing back and forth many times between mirrors provide a way for atoms to interact at essentially infinite range.  These interactions open powerful new paths for quantum simulation and quantum sensing, allowing us to leverage the certainty provided by quantum mechanics to make very precise measurements of the world around us, or allowing us to emulate one quantum system with another to provide insights and understanding. In this talk, I will provide a sampling of my group’s work including how we use the quantum measurement process and interactions to create some of the most highly-entangled states realized in any system, realize the first entanglement-enhanced matterwave interferometer, and simulate the predicted dynamical phases of BCS superconductors.

**Special Colloquium** Monday, February 17 — "The Role of Clouds in Earth’s Changing Climate"

  • Presenter: Ivy Tan, McGill University
  • Time: 11:00 a.m.
  • Location: JILA Auditorium
  • Host: Michael Ritzwoller
  • Abstract: How much will Earth warm in response to increasing carbon dioxide emissions?  Climate projections are highly uncertain yet have important societal implications.  Climate models are the most effective tools for making climate projections, however, their ability to reliably project climate has been hindered primarily by challenges in representing clouds in Earth’s atmosphere.  Cold clouds composed of supercooled liquid droplets and ice crystals are particularly challenging to represent in climate models due to the large number of complex micro-scale physical properties and processes associated with these clouds.  In this talk, I will demonstrate how satellite observations are indispensable tools for improving our understanding of cloud physical processes and improving the representation of these processes in climate models.  I will also identify the key micro-scale physical processes associated with cold clouds that are important for Earth’s changing climate through their interactions with solar and terrestrial radiation.  I will then focus on clouds in the Arctic --- a region where Earth is experiencing accelerated warming compared to the rest of the globe -- and show how nonlinear interactions between clouds, the vertical thermal structure of the atmosphere, and sea ice contribute to the amplified warming.  I will conclude with a glimpse into exciting new developments underway, including the future launch of satellite instruments and the rise of high-resolution global storm-resolving models, and explain how these advancements will enhance our understanding of Earth’s physical climate system in the coming decade.

February 19 — "Closing the Loop in Early Universe Cosmology?"

  • Presenter: Chris Smeenk, Western University, Canada
  • Host: Allan Franklin
  • Abstract: Inflationary cosmology has been widely accepted for decades. Yet there are persistent debates about inflation which raise central questions in philosophy of science. Skeptics have often expressed doubt regarding whether inflation is "testable" or "falsifiable," due to the flexibility of inflationary models. This is an instance of a general question in philosophy of science: to what extent does phenomenological success support the claim that a theory gets the physics right? How does one answer a skeptical worry, that the theory "fits the data" because it is flexible? My aim in this talk is reframe this debate, drawing on ideas from George Smith’s historical and philosophical assessment of celestial mechanics. Smith answers the skeptic by looking at the role a theory plays in guiding inquiry. Following Newton, astronomers "closed the loop" by starting with an initial description of motions; using discrepancies with observations to identify sub-dominant physical details; incorporating these details into a more refined description; and then starting the process over again. Through this process astronomers discovered hundreds of new details about the solar system, based on assuming the theory of gravity, that could be checked independently. Considering this case helps to characterize one challenge facing theories of the early universe: our lack of clarity about the underlying physics driving inflation has blocked pursuit of a similar process of iterative refinement. I will close by considering several different responses to this challenge.

**Special Colloquium** Thursday, February 20 — "Decoding the Dialogue Between Clouds and Land through Boundary-Layer Turbulence"

  • Presenter: Tianning Su, Lawrence Livermore National Laboratory
  • Time: 11:00 a.m.
  • Location: JILA Auditorium
  • Host: Michael Calkins
  • Abstract: The planetary boundary layer (PBL), the lowest part of the atmosphere, plays a key role in regulating interactions between the land surface, clouds, and atmospheric turbulence. These interactions drive the exchange of energy, moisture, and aerosols, shaping both weather and climate. However, turbulence within the PBL adds complexity to these processes, making them challenging to understand and predict. In this seminar, I will examine how PBL turbulence mediates the "dialogue" between clouds and land, with a focus on the role of surface fluxes and radiation in regulating the coupling between them. Using lidars—laser-based instruments that detect atmospheric particles such as aerosols and clouds—we developed remote sensing algorithms to determine PBL height and cloud properties, offering observational evidence into the mechanisms that drive aerosol transport and cloud formation. These observations help us investigate how cloud-land coupling influences aerosol-cloud interactions, which remain one of the largest uncertainties in climate projections. Finally, I will discuss how these findings inform climate models, with support from artificial intelligence to integrate complex data and refine simulations. By integrating high-resolution field observations with advanced modeling, this research deepens our understanding of how PBL turbulence shapes interactions between clouds and land, a key driver of weather patterns and the climate system.

**Special Colloquium** Monday, February 24 — "Turbulent and stochastic dynamics in the climate system: energy transfers, self-organization and abrupt transitions"

  • Presenter: Adrian Van Kan, University of California, Berkeley
  • Time: 11:00 a.m.
  • Location: JILA Auditorium
  • Host: Michael Calkins
  • Abstract: The Earth’s climate system is highly complex, consisting of many coupled components. Turbulent motions in the atmosphere and oceans across a wide range of spatial and temporal scales are highly important as they not only transport heat from the equator to the poles, but also distribute aerosols, nutrients and pollutants across the globe. These atmospheric and oceanic fluid flows are impacted at large scales by the Earth’s rotation, density stratification and their thin-layer geometry - for instance, the troposphere is around 10km high, but weather systems typically extend over 1000km in the horizontal direction. These factors strongly constrain the behavior of these flows, leading to striking self-organization into large-scale vortices and zonal jets. Moreover, nonlinear feedback mechanisms in this complex system lead in many cases to multiple coexisting metastable states, between which the system can transition abruptly due to intrinsic fluctuations or external (e.g., anthropogenic) forcing. An important example of this is the Atlantic Meridional Overturning Circulation, which is a tipping element in the climate system that has been abruptly shut down and re-emerged in the past. Due to the complexity of the climate system, a hierarchy of models of varying complexity is required to elucidate its properties. In this talk, I will present results from idealized models at the lower-complexity end of this model hierarchy, where key physical insights can be gleaned, namely self-organization in a turbulent dry atmosphere and abrupt transitions between large-scale, hurricane-like vortices and zonal jets or small-scale three-dimensional turbulence. I will also provide an outlook on my future work, including rotating moist convection, which is a key driving mechanism in Earth’s atmosphere, idealized climate modeling and ideas relating to climate engineering.

February 26 — "An introduction to climate engineering"

  • Presenter: David Keith, University of Chicago
  • Host: Eric Cornell
  • Abstract: It is possible to reduce some of the climate risks of accumulated CO2 by deliberately altering the Earth's albedo using Sunlight Reflection Methods (SRM) also called solar geoengineering. It is possible to remove carbon from the atmosphere at large scale using various methods for Carbon Dioxide Removal (CDR).  Estimates of the cost, risks, and efficacy of these tools will remain uncertain but it is now possible to make some policy-relevant quantitative comparisons between risks and benefits, and to speculate about the appropriate use of energy-system decarbonization, CDR, and SRM.

**Special Colloquium** Thursday, February 27 — "Oceanic turbulence regimes and their impact on the climate system"

  • Presenter: Roy Barkan, Tel Aviv University
  • Time: 11:00 a.m.
  • Location: JILA Auditorium
  • Host: Michael Ritzwoller
  • Abstract: The ocean absorbs most of the heat and about a quarter of the carbon emissions caused by human activities. These anthropogenic perturbations significantly influence the ocean circulation, with direct and critical implications for the climate system. The ocean circulation is characterized by diverse turbulence regimes that span a vast range of spatial and temporal scales. Understanding how these distinct turbulence regimes and their interactions lead to the observed spatiotemporal distributions of energy, heat, and tracers in the ocean is essential for predicting circulation adjustments and their effects on the climate system. 
    In this talk, I will discuss how the interplay between geostrophic turbulence, submesoscale turbulence, boundary layer turbulence, and wave turbulence shapes the ocean circulation, with a particular focus on energy transfer and material transport. I will also distinguish between the dominant processes occurring in the ocean’s mixed layer, where continuous interactions with the atmosphere take place, and in the deeper thermocline region. Finally, I will demonstrate how a comprehensive approach – combining analytical theory, circulation models of varying complexity, remote sensing, and carefully designed field experiments – can ultimately improve the representation of these turbulent processes in climate models.

March 5 — "From Mars Sample Return to Enceladus plume missions: finding habitable environments and life across the solar system"

  • Presenter: Jonathan Lunine, JPL, Caltech
  • Host: Mihaly Horanyi
  • Abstract: Planetary exploration has unveiled environments that could support life today, or in the past, or contain the ingredients of life. Mars was once habitable; Enceladus’ ocean is today, Europa is a question mark, and Bennu contains most of the basic key monomers of life in abiotic form. I will discuss how this all fits together. 

March 12 — "Atom interferometry: holding versus dropping atoms"

  • Presenter: Holger Mueller, University of California, Berkeley
  • Host: Adam Kaufman
  • Abstract: Atom interferometers are versatile instruments, working as quantum sensors in the field and probing the laws of physics at the deepest level in the lab. We will discuss two examples, testing the standard model by measuring the fine-structure constant and searching for quantum aspects of the gravitational field, such as superposition and entanglement.
    In typical atom interferometers, the freely-falling motion of the atoms limits the free evolution to a few seconds. We will show that atoms trapped in optical lattices allow free evolution times as long as 70 seconds, during which small effects can generate large, measurable phase shifts.  We use a system of signal inversions to suppress systematics caused by the trapping potential. This enables measuring the attractive force from a small tungsten mass with a precision that is five times improved over a previous measurement with freely falling atoms. In the future, this may yield insights into the coherence of the gravitational field itself. The long-lasting coherence lends itself well to measuring the dynamic interactions between the atoms and a coherent mechanical system, such as a torsion pendulum. A setup that is intended to take the first step is under construction.
    Our measurement of the fine-structure constant uses atoms in free fall. This isolates them strongly from environmental influences and minimizes systematic effects. It is favorable in applications that require long-term stability or absolute accuracy. Minimizing the leading systematic effects requires clean and well characterized laser wavefronts. This is hoped to improve the accuracy beyond current limitations and clarify the issues raised by the current, discrepant, measurements.

March 19 — "Scaling towards AGI"

  • Presenter: Nikolas Tezak, Open AI
  • Host: Mihaly Horanyi
  • Abstract: In this talk, I will take you on a tour of large language models, tracing their evolution from Recurrent Neural Networks (RNNs) to the Transformer architecture. We will explore how Transformers elegantly sidestep the vanishing and exploding gradient issues that plagued RNNs. I will introduce neural scaling laws—empirical relationships reminiscent of scaling behaviors common in physics—that predict how model performance improves with increased computational investment. We will also discuss different training paradigms and the key stages a model undergoes, from pretraining through deployment. I will illustrate some of the primary complexities encountered when scaling up large-model training, focusing on performance, resilience, and correctness. Finally, zooming out, I will share my personal perspective on our trajectory toward artificial general intelligence (AGI) and what to expect in the near term.

March 26 — No Colloquium, Spring Break

April 2 — "Riding the Light: How to Probe Strong-Field Effects with Flying-Focus Pulses?"

  • Presenter: Martin Formanek, MPIK, Heidelberg, Germany
  • Host: Yuan Shi
  • Abstract: Due to the exponential progress in laser technology, ultra-intense lasers are quickly becoming an essential tool for studying phenomena of quantum electrodynamics. These include e.g. radiation of accelerated charged particles, photon decay into particle-antiparticle pair, and polarization of vacuum. After a brief overview of these effects, we will discuss “Flying Focus” (FF) laser pulses which enable co-propagation of particle beams (e.g. ultra-relativistic electrons or hard photons) with the laser focus, so that they stay in the region of peak field intensity for prolonged interaction times. We will introduce FF generation methods and analytical description of FF pulses with arbitrary focal velocities and discuss experimental configurations in which the long laser-particle interaction time aids high-intensity applications. Since signatures of strong field effects in laser-particle interactions accumulate with interaction time, the FF regime enables experimental access at orders of magnitude lower laser powers and intensities than in conventional fixed-focus setups. Even more importantly, in the quantum regime of the laser-electron interaction the energy loss and photon yield scale more favorably with the interaction time than the laser intensity, giving FF an outright advantage over fixed-focus pulses.
  • Bio: Martin Stack Formanek earned his bachelor's and master's degrees from Charles University in Prague. Then he moved to the U.S. on a Fulbright fellowship which enabled him to pursue PhD in physics at the University of Arizona (Tucson, USA). After completing his degree, Martin worked as a postdoc with Antonino Di Piazza at Max Planck Institute for Nuclear Physics in Heidelberg, Germany. Since 2022, he is employed at ELI Beamlines Extreme Light Infrastructure facility near Prague, Czech Republic. At ELI Beamlines he studies strong field electrodynamics in flying focus pulses as a Marie Sklodowska-Curie fellow. 

April 9 — "Ultrafast quantum and classical nonlinear nanophotonic circuits"

  • Presenter: Alireza Marandi, California Institute of Technology
  • Host: Juliet Gopinath
  • Abstract: Ultrafast sciences and technologies are founded on the principles of ultrashort-pulse nonlinear optics. Until now, their discrete and bulky nature has hindered the utilization of their vast functionalities for many applications, ranging from sensing to computing and quantum information processing. In the past few years, nanophotonic lithium niobate (LN) has emerged as one of the most promising platforms for integrated photonics, characterized by strong quadratic nonlinearity. In this talk, I will present recent experimental progress in the realization and utilization of ultrafast nonlinear devices in nanophotonic LN, which outperform their table-top counterparts. These advancements include intense optical parametric amplification [1], ultrafast ultra-low-energy all-optical switching [2], few-cycle vacuum squeezing [3], ultrafast laser mode-locking [4], ultrabroadband coherent light sources [5, 6], and generation of two-cycle pulse [7]. I will also discuss ongoing efforts toward the miniaturization of ultrafast technologies and the development of chip-scale ultrafast nanophotonic circuits in both the classical and quantum regimes.
    References
    [1] L. Ledezma, R. Sekine, Q. Guo, R. Nehra, S. Jahani, A. Marandi, “Intense optical parametric amplification in dispersion engineered nanophotonic lithium niobate waveguides,” Optica 9 (3), 303-308 (2022).
    [2] Q. Guo, R. Sekine, L. Ledezma, R. Nehra, D. J. Dean, A. Roy, R. M. Gray, S. Jahani, A. Marandi, “Femtojoule femtosecond all-optical switching in lithium niobate nanophotonics,” Nature Photonics 16, 625–631 (2022).
    [3] R. Nehra, R. Sekine, L. Ledezma, Q. Guo, R. M. Gray, A. Roy, A. Marandi, “Few-cycle vacuum squeezing in nanophotonics,” Science 377, 1333–1337 (2022).
    [4] Q. Guo, B. K. Gutierrez, R. Sekine, R. M. Gray, J. A. Williams, L. Ledezma, L. Costa, A. Roy, S. Zhou, M. Liu, A. Marandi, “Ultrafast mode-locked laser in nanophotonic lithium niobate,” Science 382, 708-713 (2023).
    [5] A. Roy, L. Ledezma, L. Costa, R. Gray, R. Sekine, Q. Guo, M. Liu, R. M. Briggs, A. Marandi, “Visible-to-mid-IR tunable frequency comb in nanophotonics,” Nature Communications 14 (1), 6549 (2023).
    [6] R. Sekine, R. M. Gray, L. Ledezma, S. Zhou, Q. Guo, A. Marandi, “Multi-octave frequency comb from an ultra-low-threshold nanophotonic parametric oscillator,” (arXiv:2309.04545).
    [7] R. M. Gray, R. Sekine, M. Shen, T. Zacharias, J. Williams, S. Zhou, R. Chawlani, L. Ledezma, N. Englebert, A. Marandi “Two-optical-cycle pulses from nanophotonic two-color soliton compression,” (arXiv:2501.15381).
  • Bio: Alireza Marandi is a Professor of Electrical Engineering and Applied Physics at Caltech. He received his PhD from Stanford University in 2013. Before joining Caltech, he held positions as a postdoctoral scholar and a research engineer at Stanford, a visiting scientist at the National Institute of Informatics in Japan, and a senior engineer in the Advanced Technology Group of Dolby Laboratories. Marandi is a Senior Member of OSA and IEEE and has been the recipient of NSF CAREER award, the AFOSR YIP award, ARO Early Career Award, DARPA Young Faculty Award, and the Young Scientist Prize of the IUPAP. He is named the 2019 KNI-Wheatley Scholar and a 2023 Sloan Foundation Fellow. Marandi is a co-founder and a member of board of directors of PINC Technologies Inc., which is a startup company in Pasadena developing photonic integrated nonlinear circuits

April 16 — "Extreme beams and strong-field QED"

  • Presenter: Sébastien Corde, Ecole Polytechnique
  • Host: Michael Litos
  • Abstract: With today’s accelerator facilities such as the 10 GeV FACET-II facility at SLAC, extreme beam physics is emerging as a promising science area where ultrashort and dense electron beams can be used as a source of TV/m fields, enabling high field matter interaction and new applications in photon science and particle acceleration. Going beyond, many scientific opportunities arise when the beam density approaches that of a solid, of about 1023-24 cm-3 and when the field can exceed the Schwinger field in the electron rest frame, entering the strong-field regime of quantum electrodynamics (QED) where electron-positron pairs are produced from light-vacuum or light-light interactions, notably via the nonlinear Breit-Wheeler process.
    Alternatively, multi-pettawatt laser facilities also enable to probe strong-field QED by generating extreme beams in laser-plasma accelerators, that can scatter off lasers with extreme intensities.
    In this colloquium, I will present scenarios where electron beams interact with plasmas and lasers in extreme conditions, with experimental results obtained at the FACET-II 10 GeV facility in the US, at the APOLLON laser facility in France and at the ELI-NP laser facility in Romania. The first scenario is an original concept where the electron beam is focused by the beam fields reflected by multiple conducting layers that act as solid-density plasmas, with the potential to reach solid-density beams and enter the strong-field QED regime, as well as to generate electron-positron pair jets. The second scenario considers an ultra-intense laser that is used in three plasma stages to drive a laser-plasma accelerator and generate multi-GeV electrons, be boosted by relativistic laser self-focusing to extreme intensities, and finally be reflected by a plasma mirror to collide head-on with the electron beam and to trigger strong-field QED processes.
  • Bio: Sébastien Corde started his research with a PhD in Laboratoire d'Optique Appliquée at Ecole Polytechnique in France, working on the development of laser-plasma accelerators and their applications to light sources, and continued his career as a postdoc at SLAC where he carried out plasma wakefield acceleration experiments with the FACET test accelerator facility. Joining Ecole Polytechnique again in 2015, he is now Professor with a broad range of research activities and numerous achievements spanning plasma accelerators and positron acceleration, light sources and free-electron lasers, extreme beam physics and strong-field QED, as well as laboratory astrophysics and beam-plasma instabilities. He currently works on FACET-II experiments, as a Visiting Scientist at SLAC.
     

**Canceled** April 23 — "Surface and Interface Engineering for Reversible Electrochemistry"

  • Presenter: Chunmei Ban, University of Colorado, Boulder
  • Host: Joe Berry
  • Abstract: Electrochemistry involves chemical reactions that are driven by the movement of electrons and ions, typically occurring at surfaces or interfaces. A key example is rechargeable batteries, where ions migrate through the liquid electrolyte and electrons flow through the external circuit. The electrochemical reactions take place at the electrode–electrolyte interface where electrode materials receive both ions (Li+, Na+, etc) and electrons during discharging, and release them during charging, enabling the reversible storage of electricity. Thus, my research lab aims to deepen the understanding of surface and interface science to stabilize the electrode-electrolyte interface during electrochemical processes. In this talk, I will share our research focus, methodologies, and key findings, with a particular emphasis on how we design battery materials to suppress undesirable reactions and enhance performance through interface engineering. I will highlight two next-generation battery technologies: solid-state batteries and sodium-ion batteries. Solid-state systems hold great promise but face significant challenges, such as lithium dendrite propagation that can cause short circuits and cell failure. I will present our recent efforts to mitigate dendrite growth through stress-engineering and by understanding the role of grain boundaries in electrochemical performance. The talk will also cover the development of sodium-ion batteries, which offer a cost-effective and abundant alternative to lithium-ion systems.
    Finally, I will emphasize the value of interdisciplinary collaboration in advancing energy storage research, and I hope this presentation sparks conversation and future collaboration across departments.
  • Bio: Chunmei Ban is an Associate Professor at the Paul M. Rady Department of Mechanical Engineering and affiliated with Materials Science and Engineering Program at University of Colorado Boulder, Boulder, CO. Prior to 2019, Ban was a Senior Scientist (V) in the Chemistry and Nanoscience Center at National Renewable Energy Laboratory (NREL), Golden, CO, has led DOE-awarded projects in intermetallic anodes, high-energy cathodes, and direct recycling process for battery materials. Ban received a Bachelor’s and Master’s degree from the Department of Chemical Engineering from Tianjin University, China and holds a PhD in Chemistry from the State University of New York at Binghamton, supervised by Prof. M Stanley Whittingham, a 2019 Nobel Laureate in Chemistry. Her current research efforts revolve around enhancing the fundamental understanding of chemical and physical properties during the electrochemical process, with the aim of developing next-generation electrochemical materials for energy storage applications.

April 30 — "Quantum Signal Processing: Making Schrödinger Cats and Other Exotic States of Microwave Photons"

  • Presenter: Steve Girvin, Yale Quantum Institute
  • Host: Leo Radzihovsky
  • Abstract: The Schrödinger Cat idea was an early thought experiment intended to point out the weirdness of quantum mechanics. It is a paradigmatic example of the quantum principles of superposition and entanglement. With the vast experimental progress in the last two decades, we can now routinely carry out this experiment in the laboratory. In this pedagogical talk, I will present a ‘quantum signal processing’ recipe for how to create a Schrödinger Cat in a system consisting of a superconducting microwave resonator (a harmonic oscillator) and a superconducting qubit (a two-level artificial atom).  Extensions of this recipe now allow us to create even more exotic states of microwaves that can be used as quantum error correction codes.
  • Bio: After graduating in a high school class of 5 students in the small village of Brant Lake, New York and completing his undergraduate degree in physics from Bates College, Dr. Girvin earned his Ph.D. in theoretical physics from Princeton University in 1977.  
    Dr. Girvin joined the Yale faculty in 2001, where he is Sterling Professor of Physics and Professor of Applied Physics.  From 2007 to 2017 he served as Yale’s Deputy Provost for Research, overseeing strategic planning for research across Yale.  From 2019 to 2021, he served as founding director of the Co-Design Center for Quantum Advantage, one of five national quantum information science research centers funded by the Department of Energy.  
    Along with his experimenter colleagues Michel Devoret and Robert Schoelkopf, Professor Girvin co-developed ‘circuit QED,’ the leading architecture for construction of quantum computers based on superconducting microwave circuits.  
    Dr. Girvin is a Foreign Member of the Royal Swedish Academy of Sciences and Member of the US National Academy of Sciences.  He is a co-winner of the Oliver E. Buckley Prize of the American Physical Society for his work on the fractional quantum Hall effect.   In 2019, he and coauthor Kun Yang published the textbook “Modern Condensed Matter Physics” with Cambridge University Press. 

For more information about colloquia this semester, contact: Mihaly Horanyi