| Quantum entanglement is a unique physical characteristics of the quantum world,which is used to distinguish quantum world from classic world.Quantum entanglement,as an important resource in quantum information science,has been widely used in quantum teleportation and quantum dense Coding,quantum key distribution and quantum error correction.Many methods have also been proposed to describe entangled physical quantities,Such as Von Neumann entropy,negative eigenvalues of the partial and concurrence.However,it has been experimentally and theoretically proved that quantum entanglement does not contain all quantum correlation.In order to describe quantum correlation more comprehensively,quantum discord(QD)was introduced.But quantum entanglement is not exactly equivalent to nonclassical correlation.Some systems,even if quantum disentangled,still have QD,so QD causes great interest.However,the calculation of QD which does not guarantee exact results,expect some special case.In order to overcome this problem,people introduced geometric measure of quantum discord(GQD).The method of solving the two-qubits problem with this method is much simpler than QD.In this paper mainly investigates the following several respects:In chapter 1,we introduce some sorts of the typical bipartite quantum correlation,such,negative eigenvalues of the partial,concurrency and geometric measure of quantum discord.Additionally,Heisenberg spin chain system is introducted.In chapter 2,We investigate the entanglement evolution of Jaynes-Cummings model in the resonance and non-resonance cases.Our study found that the entanglement of atoms-cavity is always in the maximal entanglement state in which the initial state is the maximal entanglement,in the resonant case.In the non-resonant case,if we choose the suitable initial state,it will let the atoms-cavity be entanglingall the time.However,it will destroy the original state as the dutuning increasing.The increasing of the photon number can make the period of quantum entanglement be shorter.In the non-resonant case,if we choose the suitable initial state that could let the entanglement of atom-cavity be kept from start to finish.In chapter 3,Considering T-C model,we have used geometric quantum discord measurement method.The influence of the initial state purity,entanglement degree,the dipole-dipole coupling intensity between two atoms,and the field in the Fock state on the evolution characteristics of geometric quantum discord with time is analyzed.The result show that,the geometric quantum discord appears with periodicity.When we take a suitable initial state,the geometric quantum discord of two atoms can be kept correlation.Geometric quantum discord can be increased by increasing the intracavity photon number and the dipole-dipole coupling intensity.In chapter 4,The dynamics behavior of entanglement and geometric measure of the quantum discord in driven coupled quantum spin systems is investigated.In open quantum system,The Rabi frequency ratio of nearest qubits and different initial states and different thermal boson number are discussed.Results show that,whether the initial state is entangled or not,two qubits state will be in a stable entangled state with the time prolong,when we select the appropriate parameterη.Meanwhile,we find the quantum sudden death and quantum sudden birth phenomenon.The noise strength increasing also can make the system be in stable entanglement state.Other,we have investigated the dynamics of a the geometric measure of the quantum discord in driven coupled quantum spin systems at zero and finite temperature.Results show that,With the increase of the external Rabi frequency Ω,the GQD evolution curve shifted to the right.We also suggest control way,by the noise strength and coupling constant to approach the steady GQD. |
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