Research On Practical Measurement-deviceindependent Quantum Key Distribution System

Quantum cryptography communication?QCC?can offer unconditional security transmission of classical messages based on the fundamental laws of quantum mechanics.One of its core technologies is quantum key distribution?QKD?.Even in the presence of an eavesdropper,QKD can still allow two legitimate participants to share securely a common string of secret data?known as key?.However,due to the gap between perfect theory and real-life implementations,practical QKD systems are vulnerable to a wide variety of attacks,such as photon number splitting?PNS?attack,detector efficiency mismatch attack,time-shift attack,etc.Fortunately,measurement-device-independent quantum key distribution?MDI-QKD?can be immune to all detector side-channel attacks,which are the most important security loophole in QKD implementations.Moreover,MDI-QKD with decoy states technology can also negate the security threats of the imperfect single-photon source.Thereby,the decoy state MDI-QKD protocol is the most promising solution to the security issues in practical QKD systems.So studies on the practical MDI-QKD protocols have fundamental significance for the development and improvement of the QCC application and information security.In this dissertation,we concentrate on the design and analysis of the MDI-QKD protocols.Firstly,we briefly describe the concepts of the QCC and its development status,and make forecast on the development of the QCC technology.Secondly,the relative physical basics of the QCC are presented,which mainly include qubit,quantum logic gates,quantum states non-cloning theorem and Heisenberg uncertainty principle,quantum optical devices,BB84 and B92 protocols,and the time-reversed EPR entanglement protocol.Thirdly,we propose a two-party MDI-QKD protocol with an untrusted source based on polarization encoding by combining decoy states and the plug&play structure.Only one light source is used in the protocol,which can be controlled by an untrusted third party that even can be eavesdropper.This method not only breaks through the limitation of the key assumption that the source is trusted in initial MDI-QKD,but also overcomes a difficulty in real-life applications caused by employing mutli-lasers.The security of our protocol is built on the BB84 and the time-reversed EPR entanglement protocol.The numerical analysis results show that the proposed protocol provides a key rate that is almost entirely the same with the key rate of MDI-QKD with trusted sources in the asymptotic case.The complexity of the synchronization system can be reduced and the success rate of the Bell state measurement?BSM?can be improved in this scheme.Our work demonstrates that based on the laser and detectors shared by untrusted third party can build a quantum key distribution network.Fourthly,we propose a novel multi-party MDI-QKD based on cluster states.In this protocol,the measurement device is a four-particle analyzer which can distinguish all the 16 cluster states,and any two of four participants can build secret key bits when the measurement setup announces a successful output.We perform a security analysis for the protocol,and also derive and analyze the key rates under different values of polarization misalignment.The results show that four-party MDI-QKD is feasible over 280 km in the optical fiber channel when the key rate is about10^-6 per pulse with the polarization misalignment parameter0.015.The proposed scheme can not only be applied to a low loss system,but also can be used in the short distance range and highly loss system with a heralding and detection unit.This work suggests an important avenue for quantum network and the development of multi-party quantum communication.