Presentations
Ashok Ajoy (UC Berkeley)
Deployable, out-of-equilibrium, chemical quantum sensors
I will present our recent efforts to harness out-of-equilibrium electron and nuclear spins in molecular systems for developing highly sensitive quantum sensors. I will begin with complementary advances in semiconductor platforms—specifically NV centers and 13C nuclei in diamond—where we achieve high nuclear polarization and remarkably long nuclear spin coherence lifetimes (T2'>800 s). These features enable precision sensing of time-varying magnetic fields, with applications ranging from fundamental studies to chemical assays. Building on this foundation, I will discuss our developments of deployable chemical quantum sensors based on these spins, and applications to real-world settings.
About: Ashok Ajoy is an Assistant Professor in the Department of Chemistry at U.C. Berkeley. He is an expert in quantum sensing and magnetic resonance, and has been recognized with several awards including AFOSR Young Investigator, Camille Dreyfus Teacher-Scholar Award, and the Caldarelli, Abragam, Ampere, and Atreya Prizes in magnetic resonance.
Scott K. Cushing (Caltech)
Strong Electron-Phonon Coupling in Batteries and Solar Energy Materials
The Cushing lab focuses on ultrafast instrumentation science ranging from tabletop X-rays, to entangled photons, to new forms of battery spectroscopy. In this talk, I will briefly introduce our research areas, mentioning the increasingly "null" space explored with entangled photons, and then focus on two of the techniques – tabletop X-ray spectroscopy and ultrafast battery dynamics. For the latter, we use our newly developed, laser-driven ultrafast impedance method to investigate superionic conductors' many-body ion hopping mechanism. Picosecond temporal and spectral correlations differentiate electron-ion, phonon-ion, and potentially ion-ion interactions. Our first results on LLTO show that superionic conductivity does not occur by random thermal motion but rather by highly correlated ion-phonon modes in the THz, contrary to current ionic conductor design principles. Reducing charge density on the apical O anion using a transient charge-transfer transition also improves ionic conductivity on the picosecond timescale of optical phonons. Next, we use transient X-ray techniques to explore the complex photodynamics of the Hubbard-Holstein Hamiltonian that describes systems ranging from solar fuel materials to O-LEDs. The ultrafast X-ray pulses measure a mix of electronic and structural dynamics and, using our excited state Bethe-Salpeter equation approach, we can extract time-resolved electron and hole energies, phonon and polaron modes, and transport phenomena. We measure materials with a range of electron-phonon coupling strength versus electronic and spin correlations to map the Hubbard-Holstein Hamiltonian phase space and evaluate its predictive accuracy for new excited state materials design.
About: Scott Cushing is an Assistant Professor at Caltech with a multidisciplinary background. The Cushing lab is currently pioneering the use of ultrafast X-rays, electrons, and entangled photons for various microscopy and spectroscopy applications. Scott has been awarded DOE, AFOSR, Cottrell, Sloan, DARPA, and other early-career awards. Scott has published over 80 papers that have been cited >10,000 times.
Gordana Dukovic (CU Boulder)
Elucidating how nanocrystals drive multielectron redox chemistry
The synthetic tunability of electronic structure and surface chemistry of semiconductor nanocrystals make them attractive light absorbers for light-driven chemistry. Nanocrystals can drive a variety of photochemical transformations and they have been coupled with redox enzymes to drive reactions like H2 generation, CO2 reduction, and N2 reduction. In this talk, I will focus on our efforts to understand the properties of semiconductor nanocrystals that are essential for these light-driven transformations. Themes will include: nanocrystal synthesis, nanocrystal-enzyme interactions, interfacial charge transfer, kinetic modeling, hot electron dynamics and photochemistry.
About: Gordana Dukovic is a Professor of Chemistry and Materials Science and Engineering at the University of Colorado Boulder and a Fellow and Associate Director of the Renewable and Sustainable Energy Institute. Her lab investigates the structure, excited state properties, and light-driven chemistry of nanoscale materials.
Randall H. Goldsmith (UW–Madison)
Photonic Approaches for Single-Molecule Sensing and Spectroscopy
Photonic structures offer the ability to fundamentally alter how light interacts with matter. I will tell two stories of how these abilities can be leveraged for new ways to perform spectroscopy on molecules. In the first story, I will show how the increased light-molecule interactions in high-finesse fiber Fabry-Pérot microcavities can be used to detect and hydrodynamically profile individual biomolecules as small as single amino acids in a manner that is entirely label-free. In the second story, I will show how we are developing new fabrication routes to create highly intricate topologically non-trivial nanophotonic crystals as platforms for new forms of molecular spectroscopy.
About: Randall Goldsmith is the Helfaer Professor of Chemistry and Electrical and Computer Engineering at the University of Wisconsin Madison. He has been recognized with a DARPA young faculty award, NSF CAREER award, Alzheimer's Association Young Faculty Award, Dreyfus Teacher-Scholar Award, Journal of Physical Chemistry Lectureship, and Schmidt Sciences Polymath Award.
Ryan G. Hadt (Caltech)
Coupling Light to Molecular Electron Spins for Quantum Sensing
Spin-photon interfaces enable powerful strategies for quantum state initialization, manipulation, and readout, key functionalities for emerging quantum technologies. While these capabilities have been demonstrated in solid-state systems such as color centers and rare-earth dopants, molecular platforms remain largely untapped, despite advantages deriving from their synthetic tunability and environmental versatility. Moreover, the control of quantum states in solid-state materials typically relies on pulsed microwaves, which can limit spatial and temporal resolution compared to fully optical approaches. This talk will describe our recent demonstration of all-optical, picosecond-resolved measurements of molecular electron spin decoherence in Ir(IV) complexes under ambient, biologically relevant conditions. These capabilities enable unique mechanistic interrogation of spin decoherence processes, informing chemical design strategies to prolong molecular decoherence times by more than an order of magnitude. Additionally, this talk will discuss our ability to expand optical addressability into the tissue transparency window and probe complex chemical dynamics in solution, broadening the potential for in vivo quantum sensing. Together, these advances position molecular spin-photon interfaces as a promising frontier in quantum information science.
About: Ryan G. Hadt received his B.S. and M.S. degrees in chemistry at the University of Minnesota Duluth and his Ph.D. at Stanford University. He was a visiting postdoctoral fellow at Harvard University before continuing research at Argonne National Laboratory as an Enrico Fermi Fellow. In 2018, he joined the Division of Chemistry and Chemical Engineering at the California Institute of Technology.
Lu Wei (Caltech)
Functional Bond-Selective Microscopy in the Single Molecule Regime
Advances in optical spectroscopy and microscopy have revolutionized our understanding in live biological functions at the sub-cellular levels. In this talk, I will discuss a new mid-infrared (IR) near-infrared double-resonance imaging technique, BonFIRE, for IR bond-selective fluorescence bio-imaging with single-molecule sensitivity. This spectro-microscopy platform provides new capabilities for robust single-molecule imaging and profiling on polarization dependence, vibrational peaks, linewidths, and lifetimes; wide-field super-multiplex bio-imaging; 2D spectro-microscopy; and vibrational life-time imaging for ultrasensitive sensing of heterogeneous cellular interactions and environment.
About: Lu joined Caltech as an Assistant Professor of Chemistry in 2018. Her group works on developing next-generation vibrational imaging techniques to quantitatively investigate the intracellular biophysical and biochemical processes with an emphasis on neuronal metabolism; multiplex live-cell imaging; functional vibrational imaging and sensing with down to single molecule sensitivity.
Marissa L. Weichman (Princeton)
New Platforms for Molecular Polaritonics
In this talk, I will discuss my lab's efforts to harness optical enhancement cavities both as a platform to explore molecular physics under strong light-matter interactions and as tools for precision spectroscopy.
Polaritons are hybrid light-matter states with unusual properties that arise from strong interactions between a molecular ensemble and the confined electromagnetic field of an optical cavity. Cavity-coupled molecules appear to demonstrate energetics, reactivity, and photophysics dramatically distinct from their free-space counterparts, but the mechanisms and scope of these phenomena remain uncertain. I will discuss our new experimental platforms to investigate molecular dynamics under strong coupling. In one thrust, we are engineering polariton formation in cold gas-phase molecules, where attaining sufficiently strong light-matter interactions is a challenge and had not been previously reported. We are harnessing this infrastructure as a testbed to study fundamental polariton photophysics and chemistry. We are also searching for signatures of cavity-altered dynamics in benchmark condensed-phase systems using ultrafast transient absorption spectroscopy with the goal of better understanding exactly how and when reactive trajectories may be influenced by strong light-matter interactions.
I will also discuss our efforts in cavity-enhanced spectroscopy of complex molecular systems. Cavity-coupled frequency comb lasers enable simultaneously high-resolution, high-sensitivity, broadband, and rapid-acquisition spectroscopic measurements. We are using cavity-enhanced frequency comb spectroscopy to reveal the structure and behavior of astrochemically-relevant molecules and clusters. We are also extending these techniques towards the study of atmospherically-relevent aerosols.
About: Marissa L. Weichman is an Assistant Professor of Chemistry at Princeton University whose research interests lie in using light to probe and steer the behavior of chemical systems. Weichman obtained her BS from Caltech and her PhD from UC Berkeley. She carried out postdoctoral research at JILA/CU Boulder.