Symmetries and conservation laws in quantum trajectories: Dissipative freezing

Journal article

In driven-dissipative systems, the presence of a strong symmetry guarantees the existence of several steady states belonging to different symmetry sectors. Here we show that, when a system with a strong symmetry is initialized in a quantum superposition involving several of these sectors, each individual stochastic trajectory will randomly select a single one of them and remain there for the rest of the evolution. Since a strong symmetry implies a conservation law for the corresponding symmetry operator on the ensemble level, this selection of a single sector from an initial superposition entails a breakdown of this conservation law at the level of individual realizations. Given that such a superposition is impossible in a classical, stochastic trajectory, this is a a purely quantum effect with no classical analogue. Our results show that a system with a closed Liouvillian gap may exhibit, when monitored over a single run of an experiment, a behaviour completely opposite to the usual notion of dynamical phase coexistence and intermittency, which are typically considered hallmarks of a dissipative phase transition. We discuss our results with a simple, realistic model of squeezed superradiance.

Authors: Sánchez Muñoz, C; Buča, B; Tindall, J; González-Tudela, A; Jaksch, D

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: American Physical Society
• Journal: Physical Review A
• Volume: 100
• Issue: 4
• Article number: 042113
• Publication date: 2019-10-16
• DOI: 10.1103/physreva.100.042113
• EISSN: 2469-9934
• ISSN: 2469-9926
• Language: English
• Keywords: FFR