Entanglement Dynamic Investigation On Three-qubit Mixed States In Multipartite Cavity-reservoir Systems

Quantum entanglement is an important property of quantum mechanics, and plays acrucial role in the quantum information processing, such as quantum teleportation, quantumkey distribution, quantum dense coding and quantum computation. As is well-known, there areno perfectly closed systems in the real quantum world. The systems will decoherence due tounwanted interactions with the outside world. These unwanted interactions show up as noise inquantum information processing systems. The entanglement of the systems will decrease, andthen take place quantum decoherence. This results in the quantum state preparation andquantum operations being very difficulty in the quantum information processing. Therefore theentanglement dynamic property of quantum systems is very important in practical informationprocessing. Although the entanglement dynamic evolution of bipartite systems have beenunderstood well in many aspect, the entanglement dynamic evolution of multipartite systemsis far from dear and has many unsloved problems.In the first chapter, we introduce the entanglement measures and the phenomenon ofentanglement sudden death. In Chapter2, we recall the Kraus operator of quantumcomputation, many typical quantum channels, and the dissipative process of cavity-reservoirsystems. In Chapter3, we analyze the entanglement property of bipartite and tripartitequantum state. Furthermore we investigate the entanglement evolution three-qubit mixedstates composed of a GHZ and a W state in multipartite cavity-reservoir systems, and compareit with that of a generalized GHZ state. In Chapter4, we study the entanglement evolution ofX-form state under the dissipative process of cavity-reservoir systems. In particular, weanalyze the entanglement evolution of the three-cavity subsystems and the three-reservoirsubsystems respectively. Finally, a brief conclusion and outlook is given in the last chapter.