Characterization of Decoherence-Free Subsystems

In this paper we compare the notion of decoherence-free subsystems with the structure of the decoherence-free subalgebra for a uniformly continuous quantum Markov semigroup on ℬ ( h ) . We show that the existence of a faithful normal invariant state and the atomicity of the decoherence-free subalgebra induce a decomposition of h that allows us to identify every decoherence-free subsystem.