Composite Geometric Phase for Multipartite Entangled States

When an entangled state evolves under local unitaries, the entanglement in the state remains fixed. Here we show the dynamical phase acquired by an entangled state in such a scenario can always be understood as the sum of the dynamical phases of its subsystems. In contrast, the equivalent statement for the geometric phase is not generally true unless the state is separable. For an entangled state an additional term is present, the mutual geometric phase, that measures the change the additional correlations present in the entangled state make to the geometry of the state space. For $N$ qubit states we find this change can be explained solely by classical correlations for states with a Schmidt decomposition and solely by quantum correlations for W states.
Comment: 4 pages, 1 figure, improved presentation, results and conclusions unchanged from v1. Accepted for publication in PRA