The Scheme Of Quantum Dense Coding In Quantum Communication

Quantum information theory is a rising interdisciplinary field whichcombines classical communication and quantum mechanics. Quantum Information from the birth to the rapid development shows a very broadapplication prospects. It includes quantum communication and quantumcalculates. In quantum information theory, the most important resouroe is eatangled states. To be a potential resource for quantum information processing and the basics of quantum communication and quantum computers, quantum entanglement can be used to test basic problemsin quantum mechanics. Because of its non-locality,it can be used in many regions,especially in quantum communication. Such as quantum dense coding(QDC), quantum teleportation,quantum secret sharing(QSS) andquantum key distribution, etc. QDC is one of the important applications of quantum entanglement in quantu communication,which can transmit two bits of classical information by sending only one quantum bit. So it demonstratcd strong growth prospects. In recently years, QDC has been progressed both in theory and experiment.The first chapter, the main source, the development and the significance of quantum information theory have been discuessed in the introduction; The definition, the basic memory cell and the properties of quantum information have been introduced and the role of quantum entanglement has been research in quantum information, The advantages and disadvantages of quantum cryptography have been explained, and the knowledge of the quantum communication, the quantum computation and the quantum computer have been introduced.The second chapter, a number of concepts and principles have been introduced in the quantum mechanics, which would been involved in the quantum communication; The quantum bits, the amount of information, the Von Neumann entropy and the definition of fidelity of quantum states have been introduced. Several important one door, two doors and three doors have been given; The quantum entanglement, pure state entanglement, mixed state entanglement and the definition of entanglement measure have been introduced; The specific forms of Bell state, GHZ state and W state, and the five basic assumptions of quantum mechanics were given;Tthe principle of quantum superposition and quantum non-cloning theorem have been introduced. The third chapter, the basic idea and development of quantum dense coding and quantum teleportation in the quantum communication have been described.In Chapter 4, we propose a scheme of achieving quantum dense coding by using non-entangled W state. In this Chapter,we give two schemes:by introducing one auxiliary particle and having no participation of one auxiliary particle. to prepare the state to the expected state, we construct the necessary unitary operators and reciever get the operation sender having per--formed at a max successful probability by the collective Bell-state measurement. In these schemes, reciever get 2 bits of information. When employing partly entangled state as quantum channel, the successful probability is not 100% and the successful probability of its is decided by the least of coefficients of quantum channel.