Research On Nonlocality Of Some Entangled States In Quantum Information

Quantum nonlocality and entanglement are two of the most fundermental features of quantum mechenics, and it has been wellknown that they have many important applications in quantumn teleportation, quantum calculation etc.Especially in recent years, the research on nonlocality of quantum entangled states with continuous variable has drawn considerable attention for their successful preparationi and their realization in teleportation.In the beginning of this paper,quantum entanglement and nonlocality with the correlated theory are shown,then some research and analysis are given on two important kinds of entangled coherent states and pair cat states as following:In chapter 2, fistly a new kind of pseudospin operator is made up from a group of orthogonal basises with which the Bell CHSH operator is formed, then nonlocality of two kinds of important entangled coherent states with continuous variable is calculated; furthermore the formula of nonlocality is given when certain situation is satisfied and some simple analysis is shown on their nonlocality, finally from the master equation that the density operator satisfies in the interaction between single-mode optical field and vaccum reservoir, the evolution in a thermal reservoir of the entangled states is discussed. It is found that the nonlocality of the states is correlated with their phases, and it becomes maximal when proper phases are selected, when the amplitude is infinite.In chapter 3, the Bell CHSH operator is made from Fock states just similar to that Chen proposed in one of his papers and nonlocatily of pair cat states is calculated, then the master equation of the density matrix in phase damping model is given , from which the evolution of pair cat states in phase damping channel is given. It is shown that nonlocality of the state is correlated with the corresponding parameters, it becomes more and more weaker and even disappears finally in phase damping model while it is also related with other parameters such as the phase.The simple summary of the whole paper is given in the last chapter.