Generation Of Atomic Entanglement Via The Atom-cavity Interaction

Cavity quantum electrodynamics is an important research fieldwhich involves a single atom coupling to few optical modes. Usually,there are only one or two optical modes in a cavity and each of them canbe made to a very high electric-field intensity, thus one can realize astrong coupling between atom and optical modes. In addition, owing tothe high Q value of the cavity, photons can have opportunities to interactmany times with an atom before they leave out off the cavity. Theseproperties make cavity-QED techniques to be a particular chance forcontrolling and studying single quantum system. It also brings manychances for quantum chaos, quantum feedback control, quantumcomputation and quantum information processing.This paper mainly explores cavity-QED system in the applications ofquantum computation and quantum information processing. The contentcan be divided into four chapters:In chapter one, we introduce the quantization of the electromagneticfield and describe the interaction of the quantized field with atomicsystem. We also present some fundamental properties of quantumentanglement.In chapter two, we investigate thermal entanglement produced byresonant Jaynes-Cummings model with and without the effect ofvirtual-photon field. It is shown that there exists a critical temperature,above which thermal entanglement of atom and field mode vanishes. Inthe absence of virtual-photon field, the critical temperature increases with the increasing of the coupling constant between atom and cavity field.Thermal entanglement can be generated for sufficiently strong couplingunder room temperature. In the presence of virtual-photon field, we findthat the critical temperature is determined by the processes of real andvirtual photon transition. When the process of virtual photon transition isstronger than that of real photon transition, no thermal entanglement takesplace even if the setup is cooled to below the critical temperature.In chapter three, A scheme for preparing entangled coherent state ispresented, based on the Jaynes-Cummings model with large detaining. Wepresent a scheme for preparing the remote entangled two-particle state bylocal operation and classical communication, and discuss the influence ofrotation angle on the entanglement by means of concurrence. Finally, wegeneralize the method to the remote preparation of the entangledmulti-particle state.In chapter four, the interaction of single two-level atom withtwo-mode cavity is investigated by means of fully quantized theory,where one mode of the modes interacts with the atom through a singlephoton resonant process and the other is very far from resonance. Thedynamic behavior of atomic level occupation is surveyed in anappropriate initial state of the quantum system.