2021/05/31 by Philipp Frey, Stephan Rachel · 1 citation
Physics and Astronomy · #cond-mat.mes-hall #cond-mat.str-el #quant-ph
published as Sci. Adv. 8, eabm7652 (2022) · v3: Details regarding process tomography and additional interactions added
arxiv created 2022/01/17 · arxiv updated 2022/03/08
Novel dynamical phases that violate ergodicity have been a subject of extensive research in recent years. A periodically driven system is naively expected to lose all memory of its initial state due to thermalization, yet this can be avoided in the presence of many-body localization. A discrete time crystal represents a driven system whose local observables spontaneously break time translation symmetry and retain memory of the initial state indefinitely. Here we report the observation of a discrete time crystal on a chain consisting of 57 superconducting qubits on a state--of--the--art quantum computer. We probe random initial states and compare the cases of vanishing and finite disorder to distinguish many-body localization from pre-thermal dynamics. We further report results on the dynamical phase transition between the discrete time crystal and a thermal regime, which is observed via critical fluctuations in the system's sub-harmonic frequency response and a significant speed-up of spin depolarisation.