Quantum State Transfer In Spin Chains With Phase Shift Control

To transfer a quantum state reliably is an important task in quantum informationprocessing. For short distance quantum communication, the implement of transfer aquantum state by solid-state system attracts great attention of researchers. A spinchain is a promising candidate for the transfer of a quantum state. In this thesis, wemainly investigate the impact of the phase shift generated by the Aharonov-Casherinteraction on the transmission of a quantum state in spin chains.We study the effect of phase shift generated by aharonov-Casher interaction onthe entanglement and state transfer in a XX spin ring. We find that by controlling thephase shift, decoherence is suppressed, and the entanglement and fidelity can beenhanced. In addition, the relative positions between the sender and the receiver havean influence on the entanglement and fidelity. When they are locate at diametricallyopposite sites in an even chain respectively, we can obtain the maximum values ofentanglement and fidelity.We investigate the effect of phase shift control on the quantum state transfer viatwo parallel spin chains. We calculated the success possibility of the transmissionusing the protocol in [Burgarth D. et al.2005, Phys. Rev. A,71:052315]. The resultsshow that the probability of success can be significantly enhanced by phase shiftcontrol when the communication channel consists of two odd chains. The efficiencyof the transmission is discussed, showing that the efficiency can be enhanced in somespecific condition.All the results show that the transmission of a quantum state in the spin chain canbe improved by phase shift control. As the development of the science and technology,the method of phase shift control has extensive application prospect in the shortdistance quantum communication.