Cavity Qed, Quantum Entanglement And Quantum Information Transfer Problem

Entanglement is one of the intriguing characteristics of quantum mechanics. Entangled states are not only used to testify some basic quantum theories, but also are involved in almost every part of quantum information and play an important role in quantum information.Cavity quantum electrodynamics(QED) system not only can help us to understand quantum effects and reveal the interaction dynamics of atoms and optical fields, but also provide a effective tool for quantum information processing.In this thesis, we investigate entanglement in cavity quantum electrodynamics(QED) system. The main contents of this thesis are as follows:1. Considering two two-level atoms (A and B) initially in the EPR state, we put atom B into one cavity that is prepared in a superposition of a zero and a one Fock state. When atom B flies out of the cavity, we make an arbitrary state measurement on itThe dipole squeezing of atom A can be controlled via choosing appropriate superposition state of the initial cavity field and evolution time.2. When one of the two entangled two-level atoms interacts with a single-mode vacuum cavity resonantly, we make an arbitrary state measurement on one part of the system to control the entanglement state of the two other parts through choosing different evolution time. We investigate the evolution characteristics of the three-body entanglement and the entanglement between two parts of the system at different initial state without measurement. We obtain that all entanglement oscillates periodically. It should be noted that we can get w-entangled state via choosing appropriate initial state and interaction time. The initial entanglement information between two atoms can be transferred to the atom outside of the cavity and the cavity field at particular time.3. A scheme for quantum information transfer is proposed based on the large-detuned interaction between atom and cavity field. In this scheme thequantum information can be transferred into each other between an atom and a cavity field, many entangled atoms and a cavity field, many atoms and many cavity fields respectively.