Department Colloquium: Tuesday, September 28, 2021 - Time Crystals, the quest for a new phase of matter

Event Date: 

Tuesday, September 28, 2021 - 3:45pm

Event Date Details: 

This will be an in-person and Zoom streamed event. Attendance in-person  requires a mask at all times. 

Event Location: 

  • Broida 1640 and Zoom
  • Physics Department Colloquium

Quantum many-body systems display rich phase structure in their low-temperature equilibrium states. However, much of nature is not in thermal equilibrium. Remarkably, it was recently predicted that out-of-equilibrium systems can exhibit novel dynamical phases that may otherwise be forbidden by equilibrium thermodynamics, a paradigmatic example being the discrete time crystal (DTC). Concretely, dynamical phases can be defined in periodically driven many-body localized systems via the concept of eigenstate order. In eigenstate-ordered phases, the entire many-body spectrum exhibits quantum correlations and long-range order, with characteristic signatures in late-time dynamics from all initial states. It is, however, challenging to experimentally distinguish such stable phases from transient phenomena, wherein few select states can mask typical behavior. Here we implement a continuous family of tunable CPHASE gates on an array of superconducting qubits to experimentally observe an eigenstate-ordered DTC. We demonstrate the characteristic spatiotemporal response of a DTC for generic initial states. Our work employs a time-reversal protocol that discriminates external decoherence from intrinsic thermalization, and leverages quantum typicality to circumvent the exponential cost of densely sampling the eigen-spectrum. In addition, we locate the phase transition out of the DTC with an experimental finite-size analysis. Our results establish a scalable approach to study non-equilibrium phases of matter on current quantum processors.


 Bio: Pedram Roushan received his PhD in 2011 from Princeton University, performing the first scanning tunneling microscopy on the surface of topological insulators in the lab of A. Yazdani. After three years of post-doctoral studies in the J. Martinis lab at the University of California, Santa Barbara, in 2014 he joined the Google quantum hardware lab aiming on making a quantum computer. With the Google team in 2019, they performed the first computation on a quantum processor beyond the capability of a supercomputer. The current focus of his research is on simulating novel many-body physics with quantum processors.  


This will be an in-person and Zoom streamed event. Attendance in-person  requires a mask at all times.