Research On Quantum Secret Communication Based On Coherent State Light Source

In traditional secure communication technologies,people usually uses mathematical algorithms or mathematical problems to encrypt information to ensure the security of transmitted data.However,the security of the traditional secure communication technology depends on the computing power of the computer.With the rise and development of quantum computers and quantum algorithms,such as shor’s algorithm,people can crack the encryption technology based on mathematical algorithms in a very short period of time,thus threatening the security of transmission information.Quantum secure communication uses the Heisenberg uncertainty principle in quantum mechanics to realize the secure transmission of data,which opens up a new idea of secure transmission and has become the focus of attention and research.This paper takes quantum secure communication based on coherent state light source as the core,to study quantum noise stream cipher(QNSC)based on coherent state and high dimensional round-robin diffiernetial phase-time-shifting quantum key distribution based on coherent state,including the security analysis of QNSC against collective attacks and derivation and discussion of expression of data,running key and of the security capacity of whole system in this cases.Regarding the security weakness of QNSC system,some enhanced security technologies in digital domain have been proposed.In order to improve secure key rate and the tolerance on high noise in round-robin differential phase-shifting quantum key distribution(RRDPS-QKD)protocol,this paper propose a new version called round-robin differential phase-time-shifting(RRDPTS)protocol,in which both time and phase degrees-of-freedom are utilized to enlarge the Hilbert space dimensionality,without increasing experimental complexity or relaxing security assumptions.Compared with RRDPS-QKD protocol,RRDPTS-QKD protocol has high safety key rate in the condition of high quantum bit error rate.In addition,the experimental platform of RRDPTS-QKD protocol was built to verify the two schemes respectively.These studies have provided a solid foundation for the future deployment of quantum noise stream cioher and quantum key distribution as well as their joint cooperation.The main work and innovation achievements of this paper are summarized as follows:1)In order to solve the problem that mapping rules of single bit data in QNSC can not be directly applied to mapping of multi-bit data,this paper proposes a mapping rule of multi-bit data based on constellation rotation,which rotates the constellation of multi-bit data from different angles according to different bases,without increases of system complexity,to achieve the mapping of multi-data and improve the security of multi-data mapping in QNSC.By building the simulation model of QNSC based on Intensity Modulation/Dirtect Detection-Orthogonal Frequency Division Multiplexing(IM/DD-OFDM),the influence of multi-bit mapping based on constellation rotation under different optical signal-to-noise ratio in QNSC is discussed.2)Aiming at the problem that noise in the QNSC system has little influence on the high bit position of ciphertext and thus threatens the security of the system,this paper proposes a Bitwise NOT Operation(BNO)technology based on the parity of basis to improve the influence of noise on the high bit position of ciphertext in the QNSC system and enhance the security of the system.By building simulation model of QNSC based on IM/DD-OFDM,the influence of noise on different bit positions of cipheretext and transmission performance for Bitwise NOT Operation(BNO)technology based on the parity of basis under different optical signal-to-noise ratio is discussed respectively.3)The security of Binary Phase Shift-Keying/Quantum Noise Stream Cipher(BPSK/QNSC)based on coherent state system under quantum collective attacks hypothesis is studied.Based on quantum theory and quantum information,the security analysis model of BPSK/QNSC based on coherent state under collective attacks hypothesis is built in this paper,and the expression of the maximum security capacity of data,running key and of the whole system for BPSK/QNSC based on coherent state in this case is derived respectively.In addition,the trend of data,running key and of the whole system for BPSK/QNSC based on coherent state under different parameters are discussed.4)Due to thre lower safety key rate and tolerance on high noise in channel in round-robin differential phase-shifting(RRDPS)QKD based on coherent state,this paper proposes a new version called round-robin differential phase-time-shifting(RRDPTS)QKD based on coherent state.Compared with RRDPS,RRDPTS has a high rate of security keys and robustness to the high noise in channel.Based on different photon number states,expression of secure key rate in this case is derived.By the phase randomization theory,the derivation is extended to a general model which can be applied in practice:coherent states.Thus,the security of RRDPTS-QKD based on coherent state under collective attacks is proved and can be extended to coherent attacks.In addition,an 80 km high-dimensional RRDPTS-QKD experimental platform with 140 bit/s was demonstrated,and the trend of the secure key rate and quantum bit error rate under different parameters were analyzed respectively.