Reviving coherence and time crystals with nonreciprocal coupling
Phys. Rev. A 112, 032213 – Published 15 September, 2025
DOI: https://doi.org/10.1103/ht7n-bdp9
Abstract
The interplay between coherence, dissipation, and nonreciprocal interactions plays a crucial role in engineering novel dynamical phases of open quantum systems. Here, we consider two collective spin ensembles, each coupled to its own driven-dissipative bosonic mode, and interacting via a common dissipative bosonic field. By introducing nonreciprocity through asymmetric couplings to the shared field, we demonstrate that quantum coherence can be revived from fully decohered states. This revival signals a transition from a time-translational symmetric phase to a spontaneously time-translation symmetry-broken phase, realizing a continuous time crystal. Remarkably, steady-state entanglement emerges even in regions where macroscopic coherence is absent, underscoring the nontrivial impact of engineered dissipation. The phase transitions are characterized using numerical simulations of the full quantum master equation, mean-field analysis in the thermodynamic limit, and Liouvillian spectral properties. Our work provides a robust framework to realize coherence enhancement, steady-state entanglement, and time-crystalline behavior in driven-dissipative quantum systems.
