Investigating The Transfer Of Quantum State And The Evolution Of Entanglement In Cavity QED System

Quantum information science is the combination of quantum mechanics andinformation science. Compared with classical information science, it manifests distinctadvantages in many respects, for example, information security, operating speed,information capacity, and so on. However, diversified quantum noises, especially,decoherence induced from the system-environment unavoidably coupling will spoil thecoherence. For the system of cavity quantum electrodynamics (QED), decoherenceprocesses mainly come from atomic spontaneous emission and the decay of the cavityfield. Thus, how to suppress or use these decoherence in the cavity QED system isimportant for quantum information process. Additionally, entangled state is a powerfultool in verifying the basic problem of quantum mechanics, and it is also a significantresource for implementing quantum communication and quantum computation, so thequantitative research on the entanglement of quantum state is an important task inquantum information science.In this dissertation, we investigate how to implement some quantum informationprocesses through overcoming or utilizing decoherence processes in cavity QED, and theevolution of entanglement on the atomic system. Our main results include.1. Quantum state transfer via adiabatic passage and cavity decay. In this scheme, weadopt photons as ideal flying qubit between two cavities so that the distance ofinformation transmission is much longer. The syetem constituted by a A three-level atomand cavity evolves only in the ground dark space through adiabatic passage, so thescheme is robust against the effects of atomic spontaneous emission. And the successfulprobability of the scheme is unit in an ideal case.2. The evolution of two atoms' concurrence and the preparation of maximally entangledstate in a cavity. It discusses the evolution of concurrence on the atom system when twoatoms and a cavity resonantly interact. The result shows that we can generate a maximallyentangled state of two atoms by controlling the interact time.3. The evolution of tangle of three-atom in cavity QED system. It discusses theevolution of tangle of three-atom when three atoms and a cavity resonantly interact.