Quantum-activated switching of discrete time crystals in the mesoscopic regime

Abstract

We explore the fate of discrete time crystals (DTCs) in the mesoscopic regime, in which quantum fluctuations become relevant in the time evolution of the system. By considering the dynamics of the periodically driven open Dicke model (ODM), we observe quantum-activated switching in which the ODM jumps between the symmetry-broken pairs of the DTC. By constructing the rotating frame marginal probability distribution (RFPD) associated with the cavity mode of the ODM, we identify how quantum noise modifies the dynamics of the DTC at the ensemble level of multiple trajectories. We also elucidate the relationship between the decay of coherence of DTCs in the lab frame due to switching and the formation of a bimodal RFPD. Our work thus demonstrates the persistence of DTCs in the mesoscopic regime, and uncovers how spontaneous discrete time translation symmetry breaking (DTTSB) manifests in this regime.