Study On Entanglement Teleportation And Quantum Dense Coding Of Bipartite Systems

Quantum information science is an emerging science, which combines quantum mechanics with information science. To be a new information transmission way, quantum information science based on the basic principles of quantum mechanics, which undergoes the various coherent characteristics of quantum systems. With the ongoing of information science, it is inevitable for quantum effects,which is both challenge and opportunity. In recent years, It was shown both theoretically and experimentally that the study of quantum information science has made a great achievement. Due to the absolute security of information, the bigger of communication channel capacity and the faster of communication speed, quantum communication has attracted more and more people to study it.On the basis of previous studies, we take a small branch(entanglement teleportation and quantum dense coding) of quantum information science to study, and investigate the influence of each parameter on entanglement teleportation and quantum dense codingin different systems. In Chapter 1, it first reviews the generation,development and application of quantum information science, then the main contents and arrangement are provided. In Chapter 2, firstly,we simply introduce the quantum teleportation. Secondly, investigate the teleportated entanglement and the average fidelity properties in a system of two identical spatially separated two-level atoms in free space, and the effects of the different initial states, the entanglement of input state and the interqubit distance on the teleportated entanglement and the channel average fidelity. In Chapter 3, the teleportated entanglement and the average fidelity properties in a system of two spins under an external magnetic field and coupled to each other by a one-axis twisting spin squeezing interaction are investigated. Mainly, we study the influence of the external magnetic field, the external temperature and the entanglement of the input state on the entanglement teleportation. In Chapter 4, optimal dense coding of a two-qubit anisotropic Heisenberg XXZ model under decoherence is investigated. The results show that, to get a optimal dense coding, the decoherence rate must be enough small and the purity of the initial state must be close to 1.