Research On Engineering Of Quantum Physical Layer Secure Communication System Based On Multi-channel Frequency Coding

Quantum communication,based on the fundamental principles of quantum mechanics,offers new forms and content for secure communication.Quantum physical layer secure communication is an important branch of quantum communication that has undergone significant development over the past two decades.With the continuous development and improvement of quantum physical layer secure communication,it will further meet people’s needs for communication security,transmission speed,and application fields.In addition,the development of secure communication in the quantum physical layer will also promote the research and application of quantum mechanics,thereby providing more possibilities for scientific research and technological innovation.However,while there have been significant theoretical advancements in this area,practical implementation has faced challenges in miniaturization,systematization,and integration.To address the practical issues associated with quantum physical layer secure communication,this paper builds an experimental platform based on the single-photon quantum physical layer secure communication protocol(FRECO-DL04 protocol)and implements a multi-channel frequency encoding quantum physical layer secure communication system,laying a technical foundation for the construction of quantum physical layer secure communication network.The experimental platform achieves reliable secure communication by frequency encoding and decoding of photon polarization states.The main research contributions of this paper are as follows:1.Research on quantum physical layer secure communication protocol.Based on the dual-channel protocol(DL04 protocol),and according to the FRECO-DL04 protocol(an improved protocol of DL04 protocol)proposed by the research group,the implementation scheme of frequency-coded quantum physical layer secure communication based on polarization in optical fiber channel is designed.2.Two practical implementation methods of quantum physical layer secure communication scheme are proposed.The first method is to control the polarization state of photons by using a polarizer,and directly design the encoding and decoding via FPGA to complete the information loading and demodulation based on frequency;The second encoding method is the same as the first one,but decoding is realized by TDC and upper computer software.The first method is suitable for communication methods with small dead time and real-time communication requirements;The second method is suitable for communication methods with relatively ample decoding time and high coding rate requirements.3.A time-to-digital converter(TDC)suitable for quantum physical layer secure communication is designed and realized.To meet the time precision requirements of quantum communication,a TDC based on an FPGA is designed.Using a design approach that combines coarse and fine time measurements,the FPGA system clock is used to measure coarse time,and the fine time measurement is accomplished using an FPGA carry chain.A multi-channel TDC with a time resolution of 48.5 ps and a dead time of 60 ns is realized.