Reducing dynamical fluctuations and enforcing self-averaging by opening many-body quantum systems

This talk is based on our recent paper [1], which presents beneficial influences of a dephasing environment on many-body quantum systems out of equilibrium. Specifically, interactions with the environment can be used to mitigate dynamical fluctuations and to ensure self-averaging. Enforcing self-averaging is important, because it implies that the number of samples used in experiments and in numerical analysis can be decreased as the system size increases. We consider the survival probability (i.e., spectral form factor with a filter) evolving under different kinds of random matrices and under a spin-1/2 model with weak and strong onsite disorder. In isolated many-body quantum systems, the survival probability is non-self-averaging at any timescale, that is, the relative variance of its fluctuations does not decrease as the system size grows. By opening the system, we find that the fluctuations are always reduced, and self-averaging is ensured away from critical points.