Entangled State, Some Typical Quantum Optical System

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.Entanglement is not only a basic concept to distinguish classical world and quantum world,but also is considered a striking resource in quantum mechanies.In the field of quantum information,continuous-variable quantum entanglement which is also a very useful information resource plays a key role in quantum teleportation, quantum dense coding,and quantum cryptography and quantum computation(speed up computation in quantum algorithms,correct-error and tolerant-error).So in this thesis,we focus our research on the the entanglement dynamics for the double Jaynes-Cummings model(DJCM).The main contents of this thesis are as follows:1.We investigated the entanglement time evolution of double Jaynes-Cummings model (DJCM),where two entangled atoms A and B interacting locally with cavity fields a and b, respectively,but there are no any interactions between subsystems Aa and Bb.We consider the dynamics of pairwise entanglement via concurrence,the bipartition entanglement via negativity,and also the genuine four-partite entanglement.Our results show the entanglement evolution of DJCM from both subsystem and global perspectives.2.We have investigated the teleportation scheme for a tripartite ECS based only on linear optical devices such as beam splitter,phase shifters and photon number measurement. In the scheme,we employ the disentanglement method and take the bipartite maximal ECS as the quantum channel.It is shown that the proposed scheme can realize an almost perfect teleportation for an appreciable mean number.Compared to the previously presented teleportation schemes,the present version has some advantages.It is shown that the proposed scheme can realize an almost perfect teleportation for an appreciable mean number of photons|α|²=2,and the MAF for an arbitrary tripartite entangled state is less than unity by a quantity of the order of 10^-7.