| Quantum information science, which mainly includes quantum computer and quantum communication, has increasingly evolved as a new object. Because the carrier of information in this subject, all the problems related to information should be resolved by means of quantum theory. Therefore, quantum information science exhibits a number of advantages corresponding to classical counterpart. In the past few years, quantum information has made a surprise progress both in theoretical and experimental fields, it has created many miracles, such as absolute secure quantum key, quantum dense coding, quantum teleportation, and so on. Quantum communication is an important branch of quantum information science, and mostly involves quantum teleportation, quantum dense coding, quantum secret share, quantum secure communication.The idea of the cavity QED is to trap several atoms in a small high quality optical cavity. Quantum information can again be stored in the internal states of the atoms. The trapped atoms will provide quantum memory and optical cavities will be utilized both to perform quantum gates and to transfer quantum information. With the experimental developments concerning cavity QED, electrodynamics (QED) technique has been proven to be a promising candidate for the physical realization of quantum information processing. In this thesis, we focus our research on the applications of cavity QED to quantum information. The main results of this thesis are as follows:1. The entanglement character of two entangled atoms in Tavis-Cummings model is investigated. We investigate the entanglement time evolution of two entangled two-level atoms that interact resonantly with a single-mode field in the Fock state. The results show that the two-atom entanglement state appears with periodicity. The influence of the two-atom initial state, the dipole- dipole coupling intensity between two atoms, and the field in the Fock state on the entanglement degree of two atoms are revealed. Meanwhile the two-atomquantum state will forever stay in the maximum entangled state when the initial state is proper.2. A scheme for the teleportation of an arbitrary two-atom state in driven cavity QED has been proposed. In this thesis, we studied the teleportation and controlled teleportation of an arbitrary two-atom state in driven cavity QED. In the teleportation, the maximally two-atom entangled state are required as the quantum channel, our scheme does not involve the Bell-state measurement and is insensitive to the cavity decay and the thermal field. The probability of the success in the teleportation is 1.0.3. A protocol for implementing quantum secret sharing via EPR states in driven cavity QED. The scheme utilizes entangled atoms instead of photons as the quantum channel, which avoids the entanglement decrease in a certain degree. Message particles are not transmitted in the quantum channel during the communication process, which ensures the absolute safety of the communication. In the scheme, the cavity is only virtually excited and thus the efficient decoherence time of the cavity is greatly prolonged. Moreover, the joint Bell-state measurement is not necessary in the cavity QED. |
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