Theoretical And Experimental Demonstration Of Tomography-based Quantum Key Distribution

Quantum communication is an emerging discipline between the fields of quantum physics and information science,and is a communication method that uses quantum physical basic principle to ensure the security and privacy of the communication process.Quantum key distribution,quantum random number generation,quantum communication networks,quantum relays and quantum digital signatures are now among the research areas in quantum communication.One of these is quantum key distribution(QKD)technology,which provides unconditional security in theory,and may generate a string of security keys between two remote users named Alice and Bob through one-time pad.Quantum key distribution protocols have advanced significantly since they were first developed,both theoretically and experimentally.Quantum key distribution,one of the crucial research directions in the area of quantum communication,has its main benefit in ensuring the security of communication.However,QKD has inherent complexity and cost problems,and its communication distance and speed are also constrained when compared to conventional communication methods.Physicists and scientists have done extensive research and proposed numerous new protocols to solve these constraints.For example,the decoy-state QKD was developed to counter photon splitting attacks;the device-independent QKD can relax traditional security assumptions about devices;the measurement-device-independent QKD can be immune to all attack methods against measurement devices,which has been extensively studied because of its significant advantages in achievable transmission distance and practical security;the twin-field QKD can significantly increase the secure transmission distance.The tomography-based quantum key distribution protocol can make use of the mismatched measurements {σiσj}.With the full matrix elements,one can get a higher key rate with a tomography-based QKD protocol.In this paper,we mainly study the tomography-based QKD protocol,which is arranged as follows:1.For TB-QKD protocol,numerical simulations are performed in the amplitude damping channels,rotation channels and probabilistic rotation channels,respectively,and the TB-QKD protocol is compared with the RFI-QKD protocol.The simulation results show that the key rate of the TB-QKD protocol and the RFI-QKD protocol are equivalent in the rotation channels.However,the TB-QKD protocol obtains a higher key rate and tolerates higher noise in the amplitude damping channels and probabilistic rotation channels.2.The proposed TB-QKD protocol is firstly experimentally validated by simulating the amplitude damping channels and the probabilistic rotation channels via Sagnac interference.Four components make up the entire experiment:a quantum light source,quantum state preparation,quantum state measurement and quantum channels.Finally,experimental results show that TB-QKD protocol obtains a higher key rate than RFI-QKD protocol in the amplitude damping channels and probabilistic rotation channels.This experiment verifies the feasibility of the protocol.3.There are various system flaws in the practical QKD system,these flaws lead to vulnerabilities in the actual quantum key distribution system that may be exploited by eavesdroppers.For example,state preparation errors of light sources,light source intensity fluctuations and finite length effects,etc.State preparation errors cause the prepared state to be different from the originally expected state,which affect the key generation.The TB-QKD protocol is numerically simulated considering the state preparation errors,and the results show that TB-QKD protocol is more robust when the state preparation errors are less than 0.01.In the TB-QKD protocol,the light source intensity fluctuations and finite length effects are considered and simulated,and the results show that the light source intensity fluctuations and finite length effects will directly affect the key rate of the TB-QKD protocol.