Speaker: Carlos Sánchez Muñoz
Affiliation: Clarendon Laboratory, University of Oxford
Date: Monday, 3 June 2019 at 12:00
Location: Seminar Room, Serrano 121 (CFMAC)
The presence of a strong symmetry guarantees the existence of several steady states
belonging to different symmetry sectors. In this talk I discuss how, when the system 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 symmetry
operator on the ensemble level, the selection of a single sector from an initial superposition
entails a breakdown of this conservation law at the level of individual realizations. Since
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, typically considered hallmarks of a dissipative phase transition. We discuss
our results on a simple, realistic model of squeezed superradiance.