Influence Of Kerr Medium On Entanglement Of Cascade-Type Three-Level Atoms And A Bimodal Cavity Field

Quantum state is a very particular state at multi-particle system of quan-tum mechanics. Measuring of quantum entanglement is one of the important issue at present. In recent years, some researchers have proposed many methods to de-scribe physical quantity of entangled state, for instance, von Neumann entropy, entanglement relative entropy, negative eigenvalue of portion transpose, two qubits entanglement and three body entanglement. Because the system interacts with en-vironment unavoidably, which leads to the decreasing of the system entanglement. It is a central issue of investigation for us to enhance entanglement when the system interacts with the environment. We utilize the measurement of two qubits entan-glement and three body entanglement to investigate entanglement of the atom and cavity by evolution equation.In this paper, we investigate the influence of Kerr medium on entanglement of the cascade-type three-level atom with a bimodal cavity field filling with Kerr medium. We discuss the effect of the nonlinear Kerr medium on the atomic pop-ulation probability and the residual entanglement of the system. The results show that the nonlinear Kerr medium could change the period of the atomic population probability and residual entanglement of the system under the ideal situation. The period of the atomic population probability and the residual entanglement of the system get short, the total averages value get large, the number of the peak value increases. Meanwhile, the nonlinear Kerr medium enhances the residual entangle-ment of the system when the cavity decay is considered; the oscillation amplitude of entanglement increases with the increasing of the nonlinear Kerr constant; the resid-ual entanglement would reach a stable value with the evolution of the time. Namely, the nonlinear Kerr medium prevents the death of entanglement from occurring. Ac-cordingly, the period of the atomic population probability becomes short, the atomic probability reaches a fixed value with the evolution of the time. In addition, we also discuss influence of the nonlinear Kerr medium on entanglement between of the two atoms, we find that the Kerr medium reduces the entanglement evolution of the two atoms. The investigation of this work could provide a indispensable theory founda-tion for the future experiment.