Nonunital non-Markovianity of quantum dynamics

Abstract

Trace distance is available to capture the dynamical information of the unital aspect of a quantum process. However, it cannot reflect the nonunital part. So the nondivisibility originating from the nonunital aspect cannot be revealed by the corresponding measure based on the trace distance. We provide a measure of nonunital non-Markovianity of quantum processes, which is a supplement to Breuer-Laine-Piilo (BLP) non-Markovianity measure. A measure of the degree of the nonunitality is also provided.