Decoherence, entanglement, and chaos in the Dicke model

The entanglement dynamics in the Dicke model (DM) without rotating-wave approximation (RWA) with varied coupling parameter and initial quantum states was analyzed. The reduced-linear density entropy was use to measure the entanglement. The characteristic time of decoherence process in the early-time evolution was numerically obtained. The initial conditions were taken to be minimum uncertainty wave packets centered at regular and chaotic regions of the classical phase space for a given energy. The results show that the entanglement has a distinct change at the quantum phase transition and the entanglement for regular initial conditions is smaller than that for chaotic ones in the case weak coupling.