Non-Equilibrium Quantum Dynamics and Phases
Recent progress suggests that driven (Floquet) quantum systems can exhibit phenomena at least as rich as their static counterparts. Phases of matter that are nominally forbidden in equilibrium, such as quantum time crystals, have found new life in periodically driven systems. Observing these types of novel quantum orders, however, represents a daunting challenge as one typically expects a driven quantum system to absorb energy from its driving field, eventually heating to a featureless infinite temperature state. To this end, our group has recently been focused on understanding the time-scales associated with such heating and on providing alternate strategies to observe long-time quantum coherent behavior in Floquet systems.
One approach -- many-body localization -- represents a fruitful strategy to stabilize quantum coherent behavior without the need for stringent cooling or adiabatic preparation of low temperature many-body states. This strategy is particularly compelling in the context of symmetry protected topological (SPT) phases, which exhibit protected edge modes despite being only short-range entangled. While signatures of certain ground state SPT's have been observed in materials, directly probing their coherence properties is challenging in the solid-state setting. Realizing SPT phases in a cold-atomic quantum simulation would enable single-spin-resolved measurements of the edge modes' robustness and allow for systematic probing of the stability against perturbations. However, the requisite interaction Hamiltonians have yet to be realized experimentally. Recent results have shown that the complex interactions giving rise to an SPT phase can be emulated by modulating a simpler Hamiltonian periodically in time. Beyond enabling the emulation of a static SPT phase, modulated interactions can, in principle, give rise to intrinsically Floquet SPT's that do not have an equilibrium analogue.
Discrete Time Crystals: Rigidity, Criticality, and Realizations. Norman Y. Yao, Andrew C. Potter, Ionut-Dragos Potirniche and Ashvin Vishwanath, Phys. Rev. Lett. 118, 030401 (2017).
Floquet symmetry-protected topological phases in cold atomic systems. Ionut-Dragos Potirniche, Andrew C. Potter, Monika Schleier-Smith, Ashvin Vishwanath and Norman Y. Yao, arXiv:1610.07611.
Observation of a Discrete Time Crystal. Jiehang Zhang, Paul W. Hess, Antonis Kyprianidis, Patrick Becker, Aaron Lee, Jake Smith, Guido Pagano, Ionut-Dragos Potirniche, Andrew C. Potter, Ashvin Vishwanath, Norman Y. Yao and Chris Monroe, arXiv:1609.08684.
Observation of discrete time-crystalline order in a disordered dipolar many-body system. Soonwon Choi, Joonhee Choi, Renate Landig, Georg Kucsko, Hengyun Zhou, Junichi Isoya, Fedor Jelezko, Shinobu Onoda, Hitoshi Sumiya, Vedika Khemani, Curt von Keyserlingk, Norman Y. Yao, Eugene Demler and Mikhail D. Lukin, arXiv:1610.08057.
Many-body localization protected quantum state transfer. Norman Y. Yao, Chris R. Laumann and Ashvin Vishwanath, arXiv:1508.06995.