The Preparation Of Entanglement And Its Application In Quantum Communication

Now the development of information and science contact with all areas more and more closely. And the combination of quantum mechanics and infonnation science has become a new subject-quantum information theory. Quantum information theory is an inter-discipline of quantum mechanics and infonnation theory in the last century. Quantum information mainly includes quantum communication and quantum computation. Because of the subtle feature of quantum word, quantum information exhibits a number of advantages these do not correspond to its classical counterpart,it can effectively complete information transmitting. Quantum communication contains quantum teleportation, quantum dense coding, quantum secret sharing, quantum key distribution, remote state preparation, etc. As an interesting filed in quantum information, remote state preparation has been studied both in theory and experiment. Up to now, people have obtained some valuable results. In real life situations, most of the time, it is not possible to have a maximally entangled state to deal with quantum information schemes, thus it is worth researching quantum information schemes based on non-maximlly entangled channel. In this dissertation I mainly discuss theoretical study on preparation of entangled states and their applications in quantum communication. The thesis aims to understand some basic concepts and properties of quantum mechanics corresponding to quantum teleportation. On that basis we study on preparation of entangled states, in order that they can get better applications. This paper’s writing structure and main content is arcanged as following:In Chapter1, developing process of quantum information is reviewed, the basic conception of quantum mechanics and quantum information is introduced. The proposition and definition of quantum entanglement and kinds of quantum communication technologies which mainly contain quantum teleportation, remote state preparation, quantum dense coding, and quantum cryptography are given.In Chapter2, the protocols for generating state is proposed which mainly contain remote state preparation and preparation of photon entangled states. And we introduce the scheme of remote preparation of an arbitrary two-particle state. In the process of preparation of photon entangled states some simple linear optical elements, cross-Kerr nonlinearity and homodyne measurement are introduced. And in the end of this chapter generation of pair coherent states using weak cross-Kerr media in traveling-wave optical fields is presented.In Chapter3, The application of quantum entangled states in quantum teleportation is studied. By using a four-qubit non-maximally entangled state as quantum channel, under the condition of which’s coefficients were unknown, a scheme of an unknown three-partical state’s teleportation was proposed.In Chapter4, The full text are summarized at the end of the paper, and some possible research directions are put forward in the future...