Study On Entangled State And It's Application In Quantum Communication

Electrodynamics was discovered and formalized in the 19th century; human society was then profoundly affected by its application in the 20th century. A similar adventure is happening for quantum mechanics, discovered and formalized in the beginning of 20th century. Quantum mechanics develops acceleratory on solving microscope problems. Indeed the semiconductors technology, the laser and nuclear technology are the most common applications of quantum mechanics. However the peculiar characteristics of quantum mechanics, the nonlocality, has been realized recently and brought out a brand new science, the quantum information science. The quantum information science is an intersection of quantum mechanics and the information theory, it deals information, that is, the gathering, transporting and processing of information by means of quantum states. Among various kinds of quantum states, the quantum-entangled state is the most important one in quantum information science. 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 information.This article has several objectives. First we present the basic conception of quantum entanglement and quantum entangled states. We briefly introduce the applications of entangled state in the quantum information science, including quantum computing and quantum communication (chapter I).Secondly we study on the ways of preparing quantum-entangled states and the technique of processing information by using quantum entangled states. We discuss the technology of generating entangled photon states in detail, and then introduce the quantum teleporting and quantum state purifying method (chapter II).Then we focus our attention on the most splendid application of quantum information, the Quantum Cryptography (QC); we study different kinds of communication protocols of QC (chapter III).Finally we propose a scheme of Quantum Key Distribution (QKD) through the symmetry noisy quantum channel based on study the error rate of QKD through the channel (chapter IV).