Realization of a discrete time crystal on 57 qubits of a quantum computer (2105.06632v3)

Abstract: 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.