Research Area 01

Nonequilibrium Quantum Dynamics

Predicting and controlling the behavior of non-equilibrium many-body quantum systems is a major challenge of modern physics.  In addition to having fundamental importance for quantum statistical physics, advances in our understanding of non-equilibrium quantum dynamics have potential applications to phenomena in a broad range of fields, from materials science to quantum information. Due to their experimentally accessible timescales and exquisite spatiotemporal controllability, optically trapped ultracold atomic gases are an ideal context in which to study many-body non-equilibrium dynamics in the quantum regime. We use ultracold lithium atoms in dynamically configurable optical traps to study quantum transport phenomena, Floquet phase diagrams and Floquet prethermalization in modulated optical lattices, the role of interactions in classically chaotic quantum systems, the preparation of topologically nontrivial states and anyonic modes, and Floquet band engineering (image shows experimental data). New phenomena we have discovered with nonequilibrium techniques include controllable Floquet prethermal phases in modulated lattices, Floquet band engineering of long-range quantum-coherent transport and direct imaging of Floquet-Bloch bands, the first observation of position-space Bloch oscillations, and the first experimental realization of a relativistic harmonic oscillator. Support for our nonequilibrium dynamics research is provided by the Army Research Office via a PECASE award. Support for Floquet synthesis of anyons is provided by the UCSB-led ARO MURI.

Research Area 03

Quantum Simulation of Ultrafast Phenomena

Recent advances in ultrafast lasers promise to inaugurate a new era of tailored quantum control of electron dynamics. However, the techniques which have driven the exciting developments of the last decade are pushing up against physical limits, both on the pulse shapes, strengths, and durations that can be achieved in the lab, and on the accuracy of theoretical modeling of ultrafast phenomena. We are circumventing these limits with a radical experimental approach which is complementary to pulsed-laser experiments. Specifically, we have built a physical quantum simulator of ultrafast phenomena, in which time-varying forces on neutral atoms in a tunable optical trap emulate the electric fields of a pulsed laser acting on electrons or nuclei in a binding potential. The simulator operates in regimes equivalent to those of ultrafast and strong-field pulsed-laser experiments, opening up a hitherto unexplored application of quantum simulation techniques and a complementary path towards investigating open questions in ultrafast science. Counter-intuitively, this approach emulates some of the fastest processes in atomic physics with some of the slowest, giving rise to a temporal magnification factor of up to twelve orders of magnitude which greatly simplifies experimental access to the dynamics. In our first experiments, the correspondence with ultrafast science was demonstrated by observing sub-cycle unbinding dynamics during strong few-cycle pulses (image shows experimental data) and directly measuring carrier-envelope phase dependence of the response to an ultrafast-equivalent pulse. Support for this project is provided by the National Science Foundation.

Research Area 03

Quasiperiodic Quantum Materials

Quasiperiodicity has a profound impact on electronic structure, lying at the heart of phenomena ranging from the quantum Hall effect to topologically nontrivial materials to quasicrystals.  Important open questions regarding quasiperiodic systems range from the fundamental to the applied. Experimental investigation of these questions has been hindered by a lack of tunability: in the absence of methods for continuous tuning of incommensurability, interactions, and quasiperiodic lattice parameters, it is difficult to disentangle competing physical effects.  We are building the first fully tunable quasiperiodic quantum material for use as a model system to measure the effect of interactions and incommensurability on excitations, topologically protected edge states, and transport.  The technological basis for the proposed experiments is a tunable quantum degenerate gas in a tunable quasiperiodic optical trap.  We are using this apparatus to realize topological mass pumping, characterize quantum Hall energy spectra, and determine the effect of quasiperiodicity on the static and dynamic properties of a quantum material. Experimental data in sidebar show the first demonstration of phasonic spectroscopy in a quantum quasicrystal. Support for this project is provided by the Office of Naval Research.

Research Area 02

Alkaline Earth Quantum Gas Microscopy

Two of the most exciting recent developments in atomic physics have been quantum gas microscopy, which allows unprecedented insight into controllable quantum systems, and the production of degenerate alkaline earth gases. The continuing expansion of ultracold atomic physics beyond the first column of the periodic table to alkaline earth species such as strontium and ytterbium is opening up new horizons for the investigation of exotic quantum phases, simulation of complex materials, and quantum sensing. We are building a quantum gas microscope for high-resolution studies of ultracold strontium atoms. Support for this project has been provided by the Air Force Office of Scientific Research and the Army Research Office.

Research Area 02

Quantum Interfaces

The "second quantum revolution" now underway builds on uniquely quantum phenomena such as entanglement to obtain and process information in ways that cannot be achieved classically. The central challenge for the realization of useful quantum technologies is that the interfaces needed to control and functionalize quantum systems are unavoidably accompanied by surface-mediated decoherence, a poorly understood but ubiquitous process. Together with the groups of Ania Bleszynski Jayich and Kunal Mukherjee at UCSB and Norm Yao at Berkeley, we are pursuing a new experimental approach to this fundamental challenge by investigating controllable coupling of delta-doped nitrogen-vacancy centers in diamond to specific atomic adsorbates on an engineered quantum surface. This new experimental context will enable quantitative probing and control of surface-mediated decoherence processes, with potential implications for virtually all emerging quantum technologies. Support for this project comes from the Department of Energy.