The Research On Separability Criteria For Quantum Entanglement And Quantum Decoherence

Quantum entanglement is a very wonderful phenomenon, which is considered to be the greatest non-classical manifestation of quantum mechanics. From the view of measurements, manifestation of quantum entanglement is that measurement result of subsystem can't are independent of measurement parameters of other subsystems. The theory of entanglement tries to give answers to fundamental questions as: (1) how to detect entanglement; (2) how to reverse decoherence; (3) how to characterize, control and quantify entanglement. In this paper, entanglement detection and quantum decoherence are current research topics.The most fundamental question of theory of quantum entanglement is to determine whether the quantum state entanglement. With the development of quantum mechanical theory and quantum information technology, separability criterions have been proposed constantly. These years,lots of criterion are proposed, some of such entanglement criteria derived have relied on the bounds set by various forms of uncertainty relation. Therefore, Schr?dinger-Robertson uncertain relation is employed in deducting separability criterion in this article. Based on operators-like proposed by Duan Lu-Ming, with the help of Cauchy-Schwarz and binomial theorem, we refine the separability condition by employing the SRR instead of the HUR. By doing this, we obtain a stricter separability condition. The above idea can be expanded to general conditions, similar results can be obtained.Quantum entanglement is widely used, decoherence can bring about decrease of entanglement measures of entanglement pairs, in a worst-case scenario, the entanglement pairs will lose utilization values. Thereby, quantificational and qualitative comprehending to quantum decoherence and how to reduce the negative impact of quantum decoherence have important significance. So, it is the anther main work to investigate evolution of entanglement between atom and field and change regularity of quantum decoherence by T-C modes and linear entropy. We research evolution of entanglement between of two atom and light field by linear entropy, and briefly discuss decoherence time by using the method of decoherence time scale based on linear entropy, then we obtain the influence of the initial status of atoms on evolution of entanglement and the status of light field on decoherence time respectively.