Research On Single-Photon Quantum Secure Communication And Related Technology

In the mid-twentieth century, U.S. scientist Shannon laid theoretical foundation for cryptography, and since then modern cryptography has been developed by leaps and bounds. In the 1970s, the creation of public key system marked the birth of modern cryptography, which aroused mathematics, computer science and cryptography academic scholars' widespread concern and deep exploration. Subsequently RSA cryptosystem was put forward and the Federal Data Encryption Standard (DES) was promulgated, which created the conditions for the wide applications of the cryptography technology in the commercial, financial and other civilian uses, demonstrating a fascinating prospect.However, with the rapid development of computing technology in recent years, modern cryptography, based on the calculation safety, faces serious threat, especially when quantum computing has been on the horizon, demonstrating an ability of sweeping through the traditional cryptography system. Therefore, people began to seek for new secrecy measures. Among these measures, a method based on the quantum properties of microscopic particles to achieve the protection of information, namely, quantum cryptography, displays the brightest future. Quantum cryptography utilizes quantum mechanics to achieve secure key exchange, namely, quantum key distribution (QKD). Quantum key distribution provides traditional key exchange problems with an ideal solution, thus a combination of the two constitutes is the so-called "quantum cryptography". This new method ensures safe and reliable encryption in the quantum computer age.In this paper a variety of quantum key distribution protocols are firstly studied, and then the attacks and eavesdropping detection, security analysis of quantum key distribution and the latest progress both domestic and abroad space and fiber-optic quantum key distribution experiments are investigated. Secondly, a typical quantum key distribution scheme is selected, and key transmission rates and quantum bit error rates of fiber-optic quantum key distribution system are calculated with theoretical modeling and simulation. Thus the effects of fiber loss and dispersion which leads to a light pulse in transmission attenuation and broadening are studied, as well as the impact of single-photon detectors dark counts on the transmission distance. Also the optimum initial pulse width and the corresponding theoretical transmission distance are determined. Thirdly, implementation of communication-band infrared single-photon detectors, with InGaAs Avalanche Photodiode (APD) as a light-sensitive components, is carried out in this paper. The external drive circuit is optimized to make it work in the Geiger mode, by use of its own self-sustaining avalanche for single-photon detection. This article focuses on InGaAs APD structure, working methods, the major difficulties to overcome in the single-photon detection and the key technical issues, and meanwhile introduces the working principle, functional and circuits design and the working parameters of a prototype of passive suppression mode infrared single-photon detector.