Research On Quantum Secure Direct Communication

The development of science and technology makes human's life more and more convenient. At the same time, it also makes the security of information face more and more austere challenges. However, activities of the country, politics, business and individual cannot leave secure transfer of information. Then quantum security communication provides a new kind of secure assurance throng quantum-mechanical properties and gradually causes wide attention and deep research. As an important component of quantum communication, quantum secure direct communication can transmit secret messages directly in the process of communication and does not need to set up key in advance. So when it simplifies the communication process, it also ensures the effective and safe transmission of information. At present, the quantum secure communication has made great achievements in laboratory and practical application, our country is also expected to launch the first quantum satellite this year, so under the condition of safety, vigorously strengthening the research to improve the communication efficiency has important practical significance. In this paper, main works are summarized as follows:1?According to the foundation of quantum mechanics, quantum teleportation, quantum dense coding and quantum entanglement transfer among other mature quantum technology are introduced. And meanwhile classical BB84 protocol and ping-pong protocol are been studied in detail, including their safety and efficiency of communication.2?On the basis of the control code, this paper proposes a quantum secure direct communication scheme based on single photon. The original quantum states are prepared by receiver, the use of the control code can reduce exchange of classical information, the scheme also uses two sets of non-orthogonal quantum states. Unlike the previous protocols, the four quantum states can represent different information. So the coding capacity is 2 times that of the ralated protocols. In addition to the receiver, no one knows the initial state of quantum bits throughout the entire communication process, thus we ensure the reliable transmission of information. Under the various attacks, the scheme can effectively overcome the attacks to prove the security.3?A quantum secure direct communication scheme of high capacity is proposed by using hybrid particles. At present most protocols produced a waste throng abandoning the checking particles. In order to overcome the situation, in this protocol,the secret messages are divided into two parts firstly and then are transmitted in different ways:one part is transmitted directly with entangled particles, the other part is transmitted by single-particles after encrypted. The single-particles can also be used as checking particles. Thus the utilization rate of quantum bit is improved to 100%, and the coding capacity is 4/3 times that of the general protocols. The protocol can also make the error rate more accurate by choosing the number of the checking particles without warring about wasting problem. At the same time, the quantum entanglement properties and chaotic encryption provide the reliable guarantee for its safety. Under the use of a variety of attacks, eavesdroppers can't get any useful information. Finally being compared with several mainstream QSDC protocols, it has greatly improved the efficiency.