Abstract

A lifting is a map from the state of a system to that of a compound system, which was introduced in Accardi and Ohya (Appl. Math. Optim. 39:33–59, 1999). The lifting can be applied to various physical processes.In this paper, we defined a quantum mutual entropy by the lifting. The usual quantum mutual entropy satisfies the Shannon inequality (Ohya in IEEE Trans. Inf. Theory 29(5):770–774, 1983), but the mutual entropy defined through the lifting does not satisfy this inequality unless some conditions hold