On the existence of stationary states for quantum dynamical semigroups

Abstract

We provide two criteria on the existence of stationary states for quantum dynamical semigroups. The first one is based on the semigroup itself, while the second criterion is based on the generator which is in general unbounded and interpreted as a sesquilinear form. These results are illustrated by physical examples drawn from quantum optics. (C) 2001 American Institute of Physics.