The Dynamic Evolution Research Of Quantum Correlation

Quantum information processing, which is combined the quantum mechanics andthe information science, have developed fast over the past decades. These bring newviewpointstobothPhysicsandComputing. Inthisdissertation, wefocusonthedynam-ics evolution of quantum correlation in different decoherence models. We have knownthat the entanglement is important for quantum information processing. Recently, theresearch of quantum correlation, often measured by quantum discord, attract numerousattentions. Our works on this field are as follows:(1). We presented an analytic result for the entanglement evolution for arbitrarytwo-qubit pure state under amplitude damping and particularly phase damping channel.The disentanglement time and the relationship between it and the form of initial stateare given explicitly. The lower bounds of disentanglement time are obtained and shownto be the monotone functions of initial concurrence.(2). We reveal a relationship between the original definition of discord base on themeasurementsandthegeometricviewpointwithnoneedformeasurements,fromwhichtwo-qubit quantum discord can be described clearly. The known results about X statediscord are restated in the directly perceivable geometric language. As a consequence,thedynamicsofclassicalcorrelationsandquantumdiscordforanXstateinthepresenceofdecoherenceisendowedwithgeometricinterpretation. Wealsodiscussedthoroughlythecaseoftwo-qubitrank-twostates. Ananalyticalexpressionforthequantumdiscordis obtained by means of Koashi-Winter relation. At last, we discuss the dynamicalevolution of arbitrary 2-qubit pure states through a one-sided channel.(3). We study dynamical evolution of a solid-spin state surrounded by a nuclearspin-bathinamicro-cavity. Inthesimplifiedmodel,weassumetheinteractionsbetweenthe system spin and the bath are Ising coupling, and there is no interaction between thespin-bath and the optical field in the cavity. We also investigate quantum correlationdynamical evolutions of a two-qubit state immersed a common bath by using a Marko-vian quantum master equation, and we find the quantum discord still exist even thoughthe entanglement is absent thoroughly in the evolution.