Research Of Quantum Entanglement And Nonclassical States By Cavity QED

The cavity QED provides an effective method to deal with the interaction of light and atom, which is also one of the promising candidates for the physical realization of quantum information processing. It not only can help us to understand quantum effects and reveal the interaction dynamics of atoms and optical fields, but also provide an effective tool for quantum information processing. Quantum entanglement is the phenomenon which the classical theory is unable to explain, similarly non-classical effects, which is an important content in the quantum optics. So in this thesis, we focus our research on the entanglement character of two entangled atoms, the generation of nonclassical states and the non-classical effects of the entangled coherent light field. The main contents of this thesis are as follows:1. We investigated the entanglement time evolution of two entangled two-level atoms. The two atoms can undergo mutiphoton transition when they interact resonantly with a single-mode field in the coherent state. The results show that the two-atom entangled state evolves periodicity. The influence of the two-atom initial state, the dipole-dipole coupling intensity between two atoms, the parameter of the coherent state and the number of the transitional photons on the entanglement degree of two atoms are revealed. When the initial state is a maximum entangled state, the state of the two entangled atoms will forever stay in this maximum entangled state. So this kind of entanglement state can be used for quantum information storage.2. By using the theory of cavity QED, we study the system in which a two-level atom interacts with a cavity in the case of large detuning. Through the selective detecting of atomic state, Schrodinger cat states and entangled coherent states are easily generated. When the atom is driven by a weak classical field and the cavity filed is in the Schrodinger cat state, we study the conditions of generating the Fock states and the maximal success probability. The maximal success probability in our scheme is larger than the previous one.3. A single-mode light field interacts with a two-level atom drvien by a strong classical field, the interaction between the atom and the light field can turn into an effective anti-Jaynes-Cummings model in the strong driving and large detuning regime. This paper study two-mode entangled coherent light fields in this model, one mode of the light fields interacts with a two-level atom which is drvien by a strong classical field. During the evolution of the total system, we have a selective measurement to the atom. Through tuning the evolution time and the parameter of the coherent field which interacts with atom, we are easy to control the quantum statistical property of the light field outside of the cavity.