Geometric Phase of Mixed States in the Resonance Fluorescence Spectrum

Abstract

Berry phase of mixed state is investigated for modified Bloch equation with constant terms, which was used to explain sidebands in the spectrum of fluorescent light. The results show that for the physical phenomenon of sidebands, the Berry phases under the quasicyclic evolution exhibit as a geometric phase transition, where the transition point and region depend fully on the dynamics of population inversion and mixed degree. We find that, furthermore, the transition position is correlated to photon number. Thus the open quantum system preserves indeed a memory of its evolution in terms of the Berry phase, which may provide another clue for looking for devices of quantum memory in terms of geometric sideband approach.