The Polarization Maintaining And Polarization-basis Calibrating In The Satellite-to-ground Quantum Communication Telescope System

III Quantum communication uses the Heisenberg Uncertainty Principle and Quantum Non-cloning Theorem in quantum mechanics, and structure the protocol and algorithm based on the characteristics of quantum entanglement to realize the absolute security communication. The quantum key distribution, the quantum private key encryption, the quantum public key encryption, the quantum secret sharing, the quantum authentication and so on, are included in the quantum secret communication technology. The quantum communication has been the hot research area in the international quantum physics and information science due to the characteristics of high efficiency and absolute safety.Free-Space Quantum Communication(FSQC) based on the BB84(Bennett-Brassard 1984) protocol makes use of two groups of conjugate basis polarized photon as the carriers of information to realize the communication between the satellite and the group station. The BB84 protocol using polarized light as the coding scheme, and the contrast of polarization would have an direct affect on the communication performance of the quantum scientific experiment system. The goal of quantum scientific experiment system is to realize the transmission of quantum polarization between the optical ground station and the quantum science experimental satellite, however the optical system of ground station would make the polarization degeneration, what’s worse, the relative movement between the satellite equipment and the optical ground station would make the optical axis skewing. So the polarization maintaining and polarization-basis tracking and calibrating of telescopic optical system is the important technical problem to achieve the satellite-ground communication.For the above mentioned problem of the polarization maintaining and polarization-basis deviation, this paper made four items research as following, in order to solve the optical engineering problems in the quantum communication system and give a hand to finish the quantum scientific experiment system. 1. Introducing the BB84 Protocol and how it works, then analyzing the factors affecting the polarization contrast. And it should be focused on solving the polarization degeneration causing by opto-mechanical systems. 2. The three kinds of mathematical description model of the polarized light were established and analyzing the causes of the deviation angle of polarization-basis in order to provide the theoretical basis of the polarization maintaining technology in the optical system. 3. Analyzing and validating the feasibility of using half wave plate to calibration the deviation angle of polarization-basis. 4. Designing the the FSM scanning control software to ensure to rap telescopic system fleetly.