Research On Related Problems Of Quantum Security Direct Communication

With the development of quantum physics and modern communication technology,quantum communication technology has developed rapidly by virtue of theoretical unconditional security and efficiency.The superposition principle,uncertainty relation and uncertainty principle of quantum states provide theoretical support for the security and efficiency of quantum communication technology.At present,quantum communications mainly include Quantum Key Distribution(QKD),Quantum Secure Direct Communication(QSDC),Quantum Repeaters,Quantum Digital Signatures and other directions.The QSDC in quantum communication and Quantum Repeaters has great potential to enhance distribution efficiency and communication distance.QSDC is a way of communication of different quantum States that are directly transmitted in the quantum channel,which can raise the distribution efficiency of quantum States in communication.Quantum Repeaters can solve the problems such as the limited number of nodes and the limited transmission distance in quantum information networks.This paper focuses on the protocol design,network technology and data post-processing of QSDC.Two improved QSDC schemes are proposed to solve the problem of low communication efficiency in the existing QSDC schemes.At the same time,we put forward some improvement schemes for the existing quantum information networks.We have solved the problems of the existing quantum network schemes,such as weak anti-interference ability and limited transmission distance.Finally,considering the non ideal of component and channel,the secret information of the two parties is not consistent.We introduce the error correction process of LDPC code into the communication process,and verify the error correcting process of LDPC code.The main research contents are as follows:(1)We propose a high-dimensional QSDC scheme based on W state.By replacing the detection particles in the scheme as W state and introducing the high-dimensional quantum state as the transmission state,the theoretical analysis shows that the detection eavesdropping rate in the W state is 6% higher than that of the extended GHZ.(2)The QSDC scheme of controlled state is proposed.In order to improve the efficiency of data transmission and the controllability of the transmission process.Multidimensional quantum states are introduced into the controlled QSDC protocol.In the scheme,Bob can recover secret information successfully when Charlie permission is obtained,and Bob can not recover secret information without Charlie permission.Theoretical analysis shows that the detection rate of eavesdropping in high dimensional particle states is 11% higher than that of two-dimensional particles.(3)We propose a Quantum Repeater transmission scheme with fault avoiding transmission function,the Quantum Repeater of this design can effectively avoid the influence of noise on the transmission of information,so that others Quantum Repeater can recover the unknown information smoothly,improving the reliability of transmission in noise the quantum channel.(4)We study the quantum error correcting codes with application of quantum noise in quantum network.When a quantum bit or phase reversal error occurs in a quantum network,we can use the useful information in the check matrix corresponding to the quantum parity check code to analyze the error location,and then make the proper unitary operation of the error bits,which can increase the reliability of the communication process.(5)Because of the interference is not ideal factors,the receiver also needs to process the received information.We introduce the error correction process of LDPC code into the communication process,and simulate the performance of BP iterative decoding algorithm,MS decoding algorithm and OMS decoding algorithm under the same conditions.Finally,the relationship between codeword error rate and scheme efficiency is compared through simulation experiments.