Free-Space Quantum Cryptography And Faraday Anomalous Dispersion Optical Filter

Quantum cryptography is an emerging technology for security communications. Based on the basic principles of quantum mechanics, it resolves the crisis faced by traditional cryptography and becomes a new focus of the scientific research.In the experimental projects of QKD (Quantum Key Distribution), the free-space QKD is remarkable for the recent rapid improvements in experiments and the wide application outlook. Inthis paper, the process of free-space QKD and the application of Faraday anomalous dispersion optical filter are studied.The major work is as follows:1. From the basic principle, we introduce the developmentsfrom traditional cryptography to quantum cryptography.A review is presented about the prevalent protocol ofquantum key distribution and its current experimental research, especially, the development and new achievements of the free-space QKD.2. The theoretic calculation of the Rb Faraday anomalous dispersion optical filter (FADOF) is given in the approximation of weak magnetic field. And an Rb FADOF that operates on low light intensity is studied with the single photon detector.3. We established a free-space QKD experimental system. Acomputer produced two random synchronous digital signals; a buffered period counter was programmed; the instruments (acoustic-optic modulator, single photon detector)interfacing to the computer were accomplished; and theprogram of key-sifting routine over a public channel was implemented.