Study Of Quantum Teleportation In Cavity QED

This thesis investigates the teleportation of two-level atoms state in a vacuum cavity simultaneously interacting with a single-mode cavity field. And we also discuss the teleportation of two-level atoms in the thermal cavity simultaneously interacting with a single-mode cavity and driven by a classical field. Moreover, we complete approximate conditional teleportation of cavity mode entangled state.Quantum information is based on the quantum state. It realizes the management of the quantum information by the preparation and operation of quantum state. Nowadays, cavity QED is considered as the most important and promising protocol. Its main idea is that we can store the quantum information in the atom of energy state, making the atom restrict in the high Q cavity. Owing to the atom and cavity mode field coupling, it leads to the interaction of the atoms, and then the whole system happen the evolution of state. So we can realize the operation and preparation of quantum state, and the teleportation of unknown quantum state in cavity QED.Firstly,we have investigated the problem of teleporting a three-atom entangled W state and propose two schemes based on entanglement swapping to complete the teleportation. We put forward the first scheme for the teleportation of W state by using an EPR pair and a GHZ state via vacuum cavities,the second scheme for teleporting W state by using two EPR pairs as quantum channels and introducing an addition atom via thermal cavities. But it can be achieved by performing the Control-not operation on the corresponding to the state of atoms. And we compare with its conditions and total probability of there methods. Further more, the distinct advantage of the present schemes are that the Bell-state measurement is not required. The effects of cavity decay and thermal field are all eliminated.Next, we propose a scheme for approximate and conditionally teleporting cavity mode entangled state to another cavity in cavity QED. The scheme can be generalized to not only the teleportation of the state of a cavity mode to another mode but also the teleportation of the state of a trapped ion. It does not involve the Bell-state measurement and an additional atom is unnecessary, which is based on the resonant interaction between atom and cavity. Moreover, we also have considered the time spent, the fidelity and the success probability for this teleportation.