Entangled Coherent States Of Quantum Information Science Research

Quantum information theory is new research field that brings together disciplines of quantum mechanics and information science.Quantum information science takes many advantages which classical information science does not have.For example, improvement of the operation speeds,security of the information,increase of information capacity.In the past few years,a surprise progress is made both in theoretical and experimental fields,which has attracted much attention of people. Quantum communication is a very important branch of quantum information.At present,it mainly contains quantum teleportation,quantum dense coding,quantum key distribution,and so on.Quantum teleportation is one of the most attractive fields in quantum communication.Note that quantum teleportation,originally proposed by Bennett et al in 1993,has developed into a significant and vigorous field of research over the past decade.Quantum teleportation is one of the most striking fields in quantum communication,and also a novel and interesting application of quantum mechanics as well as the essential element of quantum communication and quantum computation.According to that the eigenstates of applied quantum systems,are with discrete or continuous spectrum construction,quantum teleportation is divided into two types of discrete variables(DV) and continuous variables(CV).Recently,great interest has been absorbed to study quantum information in continuous variables Hilbert spaces.We also make some study in this field.The study on quantum teleportation is very meaningful not only to the development of quantum communication,but also to apprehending the inside of quantum mechanics more deeply.In this Mh.D thesis,I am going to present the theoretical achievements on CV entanglement teleportation and quantum swapping which were completed during the study for my Mh.D degree.The accomplish theoretical investigations on CV quantum teleportation are based on utilizing the linear optical devices such as beam splitters, phase shifters and two-mode number measurements.The completed creative works are as follows:1.We investigate the problem of teleportation of tripartite coherent entangled state(ECS) using linear optical devices such as beam splitters and phase shifters.The scheme is based on the maximally four-partite ECS with bipartite maximal entanglement as the quantum channel to teleportation tripartite ECS.We also generalize the tripartite scheme into multipartite case. 2.We propose an effective scheme for the quantum teleportation of tripartite ECS.The scheme is based on the bipartite maximally ECS and the tripartite ECS with bipartite maximal entanglement as quantum channels.Compared to the previously presented teleportation schemes,our scheme is more experimentally realizable with the current technology.3.We present a realistic scheme for the entanglement swapping of continuous variable,in which the bipartite maximally ECS and the tripartite ECS with bipartite maximal entanglement serves as the quantum channels.It shows that for mean number of photons equal to 2,the total minimum of average fidelity for successful swapping an arbitrary tripartite ECS is 0.98.