Reversal of relaxation due to dephasing environment

Abstract

We show that any finite quantum system $S$ can be coupled to a dephasing environment in such a way that the internal mechanism responsible for relaxation of observables acting on $S$ can be effectively canceled. By adjusting this coupling, the difference between the initial and the long--time expectation values of any observable on $S$ can be tuned to arbitrarily small however nonzero value. This statement is exemplified and visualized by numerical studies of relaxation in a generic one-dimensional system of interacting fermions.