In this paper,the energy spectrum of the two-photon Jaynes-Cummings model（TPJCM） is calculated exactly in the non-rotating wave approximation（non-RWA）,and we study the level-crossing problem by means of fidelity.A narrow peak of the fidelity is observed at the level-crossing point,which does not appear at the avoided-crossing point.Therefore fidelity is perfectly suited for detecting the level-crossing point in the energy spectrum.
In this paper, the quantum entanglement between a single mode binomial field and a cascade three-level atom is calculated mechanically without the rotating wave approximation. The numerical results indicate that the quantum entanglement at the first few periods is reduced notably due to the fact that the atom is initially in the superposition state. With increasing field parameter 17, the period of the entanglement evolution becomes obvious and the quantum decoherence phenomenon emerges in a short time.
By the method of coherent-state orthogonalization expansion,the atomic inversion and the anti-bunching effect in a two-level atomic system interacting with binomial state field are studied under the Jaynes-Cummings model without rotating wave approximation.The influence of the parameter and the detuning on the anti-bunching effect are discussed,and the anti-bunching effect is also discussed under the conditions of strong coupling.Our studies show that the second order coherence degrees are quite different between the situations of with and without-rotating wave approximation.For the latter when the detuning increases,the duration of the bunching effect increases at the beginning and then decreases,and finally the light field displays anti-bunching effect completely.
JIANG DaoLai,REN XueZao,CONG HongLu & LI Lei School of Science,Southwest University of Science and Technology,Mianyang 621010,China
This paper investigates the influences of atom field coupling and dipole-dipole coupling for atoms on the entanglement between two atoms by means of concurrence, The results show that the sudden death occurs when the atom field coupling is strong enough, and the collapse and the revival appear when the dipole-dipole interaction is strong enough.
