Preparation Of Entangled States And Their Application In Quantum Communication

The quantum informatics is an intersection of quantum mechanics and the information theory, arisen from 1980s. Over the last two decades, there has been rapidly development in the theoretical and experimental study of the field. Entanglement states are recognized nowadays as a key ingredient for quantum information. We can dare to say, no quantum entanglement phenomena, no quantum information of today. Study on the quantum-entangled states can help us to understand the peculiar feature of quantum mechanics and help us to develop new applications in quantum in information.Our article mainly discussed the preparation of entangled states and the application of entangled states in quantum communication, including practical scheme for remote state preparation of a photon-photon entangled state, generation and concentration of multi-atom entangled states, practical protocol for telecloning quantum states and protocol for multi-party superdense coding by using multi-atom in cavity QED.This article has several objectives. In chapter â… , the basic conception of quantum entangled states and our basic working model are presented. Firstly, the proposition and definition of quantum entangled states, EPR paradox and Bell inequality, and several kinds of entangled states, as well as their properties, are given. Secondly, the measurement of the degree of quantum entanglement, quantum no-cloning theorem, and manipulation of quantum entanglement are introduced. Finally, the basic working model of our article is elaborated.In chapter â…¡, we study on the ways of preparing quantum-entangled states in cavity QED, including practical scheme for remote state preparation of a photon-photon entangled state, and generation and concentration of multi-atom entangled states. Among various kinds of quantum states, the quantum-entangled state is the most important one in quantum information science. So the preparation of entangled states is the prerequisite for utilizing entanglement, and has been paid much attention both theoretically and experimentally.In chapter â…¢, we focus our attention on the application of entangled states inquantum communication. A protocol for telecloning a quantum state to M distant users is proposed, via a (M + l)-particle W state. And we present a scheme for multi-party superdense coding by using multi-atom in cavity QED. In particular, both Bell-state and GHZ state measurements in our protocols can be achieved by detecting atoms separately.