Relation between geometric phases of entangled bi-partite systems and their subsystems

Abstract

This paper focuses on the geometric phase of entangled states of bi-partite systems under bi-local unitary evolution. We investigate the relation between the geometric phase of the system and those of the subsystems. It is shown that (1) the geometric phase of cyclic entangled states with non-degenerate eigenvalues can always be decomposed into a sum of weighted non-modular pure state phases pertaining to the separable components of the Schmidt decomposition, though the same cannot be said in the non-cyclic case, and (2) the geometric phase of the mixed state of one subsystem is generally different from that of the entangled state even by keeping the other subsystem fixed, but the two phases are the same when the evolution operator satisfies conditions where each component in the Schmidt decomposition is parallel transported.