Research Of Measurement-Device-Independent Quantum Key Distribution

With the research and development of enhancing computing capacity and quantum computer, the classical cryptography based on the computing complexity would hard to ensure the communication security. In contrast, the quantum key distribution(QKD)which based on the quantum physics mechanism has been proved unconditional security in principle. As a consequence, QKD will be the most efficient method to guarantee the communication security. However, the practical QKD system nowadays has a big gap between the ideal goals. For example, the key generated rate in the QKD system is still low which is hard to support video signal transmission. Moreover, the imperfection of practical devices threat the security of the real-life QKD systems. The QKD system just completes the point-to-point communication, but the research of quantum networks is on the road.This thesis focus on the research of measurement-device-independent quantum key distribution(MDI QKD). The main research points are as follow.1. We propose an experimental scheme of MDI QKD based on path coding.Measurement-device-independent quantum key distribution protocol is based on the Bell state measurement. Alice and Bob prepare one of four states randomly and send to the third party to do the BSM. Since MDI QKD proposed in 2012, there are several experimental schemes proposed to verify the correct and security of MDI QKD. In this paper, we propose another scheme based on path coding. The generated key rate is double than the phase coding based on the similar structure.2. We improve the information blind reconciliation protocol to a gradual iteration one.Information blind reconciliation protocol realizes the coding bits reconciliation without error estimation in advance. However, when the error rate is lower, the efficiency of the protocol would be not better enough, while, the iteration number is larger when the error rate is higher. To overcome these shortcomings, we propose the improved protocol to enhance the efficiency in low error rate and decrease the number of iteration in high error rate.3. We propose a structure of quantum networks based on passive optical networks.In the passive optical networks, the devices will not increase the power of transmitted signals which is a natural advantage in terms of quantum signal. In return, the unconditional security keys generated by QKD system make contribution to the security transmission. By building two disjointed quantum channels, we propose a quantumnetwork based on passive optical network with the help of MDI QKD. Even though the existence of weakly trusted repeaters, the security of the network can be guaranteed by network coding.