The Entanglement Of The Multipartite Quantum System And Its Applications

In this paper, firstly starting from the entanglement of bipartite system, we consider the Heisenberg XYZ model and investigate the influence of the parameter of the system to the entanglement. The analytic expression of the system's concurrence is obtained, which decreases with the increase of temperature and reaches its maximal value 1 while T 0. It is also shown that the ground state is the maximally entangled state. Besides, the maximal concurrence of the degenerate cases is calculated.Secondly, the influence of temperature and the number of qubits to the entanglement is discussed in the frame work of quantum Heisenberg XX model., The results show that the parity of the number of the qubit has the great influence to the properties of the entanglement. For the odd qubit system, the entanglement doesn't exist in the anti-ferromagnetic region, and the critical temperature increases with the increase of the numbers. While for the even qubit system, the entanglement exists in both the anti-ferromagnetic and the ferromagnetic regions, and the critical temperature decreases with the increase of the numbers. Specially, the influence of temperature and the impurity to pairwise entanglement is discussed for the three-qubit system, the analytic expression of the concurrence is derived. We find that the entanglement between the impurity and the normal site is very luxuriant, in some degree, the entanglement can be managed by changing the parameter of the impurity.Thirdly, the common entanglement of the multi-partite pure state is considered, the measure of it is also showed. Both the commonly entangled state and the completely state has only one form.Finally, the correlative experiments of the entanglement are simply introduced.