Research On Continuous Variable Quantum Key Distribution And Authentication Technology

The continuous variable quantum key distribution(CVQKD)and authentication technology,as an important branch of the quantum secure communication system,have built a new secure and effective communication system.In CVQKD systems quantum information can take a continuous range of values,such as position and motion quadrature of mode in continuous coherent electromagnetic fields.It has good application prospects and important research significance and the merits of higher secret key rates and less cost and infinite effectiveness of the detector.Therefore,it has a good application prospect and important research significance.Quantum authentication technology is an important prerequisite for the realization of quantum key distribution,and ensures the authenticity and reliability of identity,message and channel in the key distribution process.Squeezed light and entangled light sources in continuous variable regime are very sensitive to optical fiber loss,and it is difficult to realize the quantum key distribution task of long distance fiber system.Gaussian-modulation coherent state is the focus of research in long distance stable distribution CVQKD system.The existing theories and experiments show that the Gaussian-modulation odd coherent state can improve the performance of the key distribution system and extend the security distance.In long distance CVQKD system the degradation of polarization can affect the bit error rate and key generate rate.Effective control of polarization degradation technology is key technology.Measurement device independent(MDI)protocol can remove the sideband attack of the quantum system.Quantum identity authentication schemes combined via MDI protocol has higher security and application value.In the dissertation we have research on the transmission performance and practical security of CVQKD system,and odd coherent state in continuous variable regime,quantum identity authentication and channel authentication.The main results are listed as following.1.Gaussian modulated CVQKD protocol using odd coherent state is proposed to resolve short distance transmission problem.In this scenario logarithmic negativity between two mode entangled odd coherent states is analyzed.In perticular the scheme and procedure are depicted,and then security performance is analyzed in entangled-based model.The results show that entanglement degree of two modes odd coherent states is increased,and the renewed scheme can extend transmission distance and enhances the tolerance of excess noise in same parameter in CVQKD system.2.In order to solve the problem of low key rate in CVQKD system,a transmission scheme of CVQKD system based on orthogonal frequency division multiplexing(OFDM)technology is proposed.The scheme realizes the orthogonal frequency division modulation and demodulation between multiple channels by subcarrier,which means that the system starts with the fast Fourier transform to the quantum carrier,and the receiver carries on the Fourier inverse transformation to the quantum carrier.Secondly,the performance of the or-thogonal frequency division multiplexing of CVQKD system is analyzed,and the covariance matrix,the security key rate and the gain are calculated.The results of numerical simulation show that the orthogonal frequency division multiplexing technology can effectively improve the pulse bit rate in CVQKD system.3.Quantum identity authentication scheme via measurement device independent protocol is presented to enhance the security of authentication tehnology.Firstly authentication centers(AC)and authentication users share the identity authentication information and the authentication key.Then,the encrypted information is transmitted to non-trusted third party for the interferometry.The authentication center then judges the legitimacy of user’s identity information and updates the authentication key by comparing the results of the measurement.The scheme is depicted and security performance is analyzed in detail.The results show the renewed scheme can realize can implement identity authentication between different users.4.To solve the problem of poor stability of CVQKD optical path.In this paper,the nonlinear polarization of long distance optical fiber is studied.Simultaneously the scheme the polarization degradation of Gaussian modulation coherent light source is analyzed in quantum polarization encoding communication system.The change of channel capacity is discussed in the condition of nonlinear polarization deterioration.And control method of nonlinear polarization deterioration is proposed.The results show that the control of polarization degradation can reduce the polarization jitter m and optimize performances in the long distance CVQKD system.5.In order to enhance security of channel in quantum secure communication system,the quantum channel authentication scheme under symmetric cipher framework is studied.The scheme realizes the non-demolition detector technology of Bell state via weak cross-Kerr nonlinearity of quantum teleportation.First,quantum control gate is constructed which is used as the entanglement state to describe the shared quantum channel.By comparing the results of non-demolition detector(QND),security authentication of shared quantum channel by two parties is realized.The security performance of quantum channel authentication is analyzed in theory.The result shows that the proposed scheme can make use of the channel transmission performance to achieve perfect authentication of the quantum channel.