Quantum Correlations in Multipartite Quantum Systems

Abstract

This work is mainly based on the study of quantum entanglement (QE) and multi partite quantum correlation (MPQC) in many two-level atomic systems (TLS). QE and MPQC play a pivotal role in quantum computing and quantum information processing. Wehave computed the global quantum discord (GQD) and von Neumann entropy (VNE) of a multipartite system consisting of a TLS that interact with a eld prepared in a single mode. We use the extended Tavis-Cumming model. The e ects of intrinsic decoherence (ID) on the dynamics of the GQD and VNE are also investigated. We have extended the results for a large photon number n in the system. We have studied the e ect of change in the size of the system on the maximum value of GQD and VNE and we have also esti mated the scaling coe cients for this behavior. Moreover, the inuence of the non-linear Kerr medium (NLKM) on the MPQC and entanglement in two, three and four TLS is also explored. The NLKM has a profound e ect on both quanti ers, the GQD and VNE. For the higher values of the Kerr parameter, it is observed that the GQD and VNE show rather periodic behavior. We also consider the case of moving atoms. Both the quanti ers, the GQD and the VNE show periodic behavior, and the results are consistent with previous studies. The e ect of the NLKM is also studied on the dynamics of the system in the presence of a single-mode coherent eld. The collapses and revivals of the GQD and VNE are observed for various values of the Kerr parameter. Moreover, it is found that by increasing the values of Kerr medium parameter, the magnitude of the revivals of QE is suppressed. It is also noted that for mixed states the GQD shows comparatively damped oscillations as compared to the pure states. It is important to point out that by increasing the average number of photons in the multipartite quantum system, the GQD and VNE exhibit damping behavior. Furthermore, the revival time of both the GQD and VNE increases with the increase of NLKM parameter, for the systems with a relatively large number of atoms. Finally, we investigated the inuence of Stark shift on the system consisting of two, three and four TLS interacting with a single-mode Fock and coherent eld in the cavity. The dynamics of the GQD and VNE in the presence of Stark e ect indicates that the MPQC decrease with the increase of the Stark parameter for both the Fock and coherent eld. In a nutshell, our work gives a comparison between MPQC and entanglement for a many TLS interacting with single mode eld under the inuence of di erent environments