Research On Effects Of Inhomogeneous And Multi-Impurity Of Heisenberg Spin Chain On Entanglement

The quantum information is a new cross field which combined the quantum mechanics with the information theory. The quantum entanglement is a very important resource for quantum information; therefore, with the birth and development of quantum information, it is unavoidable that most of the researchers pay their attention to quantum entanglement. Recent years, there have been many kinds of study results about quantum entanglement. The study on quantum entanglement is a frontal and popular direction of quantum theory because quantum entanglement will decide whether the future quantum computer can be created.This dissertation contains four chapters. In the first chapter, we have comprehensively introduced the definition of quantum entanglement and some measures of quantum entanglement. Furthermore, we have also shown the recent researches on this aspect. There are our main works of this dissertation in the second, third and fourth chapter. We have studied the effect of multi-impurity on the entanglement between nearest-neighboring two qubits of Heisenberg ring in the second chapter, and then we have shown the role of impurities in improving quantum entanglement. In this chapter, we have concerned different situation of nearest-neighboring impurity and non-nearest-neighboring one, and the different number of impurity put in the ring. In the third chapter, we have described the effect of time-dependent couplings, and at the same time we have also thought the effect when there is decay in the system. In the last chapter, namely the fourth one, we have studied the entanglement of anisotropic Heisenberg XYZ ring under inhomogeneous magnetic field.