LAUSR

We have studied entanglement entropy and Husimi Q distribution as a tool to explore chaos in the quantum two-photon Dicke model. With the increase of the energy of a system, the linear entanglement entropy of a coherent state prepared in the classical chaotic and regular regions becomes more distinguishable, and the corresponding relationship between the distribution of time-averaged entanglement entropy and the classical Poincaré section has clearly been improved. Moreover, Husimi Q distribution for the initial states corresponding to the points in the chaotic region in the higher-energy system disperses more quickly than that in the lower-energy system. Our results imply that higher system energy has contributed to distinguishing between the chaotic and regular behavior in the quantum two-photon Dicke model.