Kinematic approach to off-diagonal geometric phases of nondegenerate and degenerate mixed states
arXiv:quant-ph/0405048 · doi:10.1103/PhysRevA.71.032106
Abstract
Off-diagonal geometric phases have been developed in order to provide information of the geometry of paths that connect noninterfering quantal states. We propose a kinematic approach to off-diagonal geometric phases for pure and mixed states. We further extend the mixed state concept proposed in [Phys. Rev. Lett. {\bf 90}, 050403 (2003)] to degenerate density operators. The first and second order off-diagonal geometric phases are analyzed for unitarily evolving pairs of pseudopure states.
New section IV, new figure, journal ref added