Indexed on: 11 Nov '16Published on: 11 Nov '16Published in: arXiv - Quantum Physics
Open quantum systems usually reach a unique stationary state with ergodic dynamics. In other words, the ensemble averages and the time averages of the expectation values of open quantum systems are usually the same for all quantum trajectories. Although open quantum systems are in general ergodic, many classical stochastic processes are not. Hence if classical physics emerges from microscopic quantum models, there have to be mechanisms which induce non-ergodicity in open quantum systems. In this paper, we identify such a mechanism by showing that quantum feedback dramatically alters the dynamics of open quantum systems, thereby possibly inducing non-ergodicity and a persistent dependence of ensemble averages on initial conditions. As a concrete example, we study an optical cavity inside an instantaneous quantum feedback loop.