The Research And Realization Of Quantum Experiment Control Unit On Satellite Based On FPGA

Quantum information science formed from the combining of classical information science and quantum mechanics, which has expended greatly recently. Quantum information science has been studied extensively, because of its great prospects and advantages compared to the classic information science.Quantum communication is one of the most mature research directions before practical application. So far optical fiber-based quantum communication is comparatively mature and has been put into application. However, it is difficult to achieve long-distance quantum communication, as a result of the attenuation of fiber and unknown irregular environment. Therefore, it is necessary to realize the satellite-to-earth quantum communication, in order to complete global quantum key distribution, long-distance quantum entanglement distribution and quantum teleportation.Experiment control unit plays an important role in satellite-to-earth quantum communication; it is a key factor to complete the experiment. Thus research and realization of it is of great significance. This work is mainly about the research and realization of the satellite quantum experiment control unit based on FPGA. The main tasks of the quantum experiment control unit include: quantum signal sending control, quantum signal arrival time measurement, scientific data transmission and storing. Signal sending control and time measurement are the focus and innovation points of this paper. With weak coherent light as information carrier in quantum communication, the receiver can only detect a few signals because of the attenuation of satellite-ground quantum channel. To increase the number of detected signals, it is necessary to improve transmitted frequency. Transmission rate can achieve 200 MHz by cyclic pulse modulation in this study. And high-precision time measurement is an essential part to detect high-frequency signal as well as mitigate noise disturbance. We achieved time measurement by FPGA carry chain, which with precision less than 50 ps. Satellite quantum experiment control unit consists of five modules which include: LD modulation module to control quantum signal sending; time measurement module to detect the arrival time of quantum signal; data bus control module to transmit scientific data; SDRAM control module to store the data; and instruction parsing and system control module used to take charge of task scheduler of each module. By using quantum experiment control unit, we conducted experiments on quantum key distribution, quantum entanglement distribution and quantum teleportation respectively. The code rate and bit error rate of quantum key distribution are 1.8kbs and 2.8%, when the attenuation is 40 db. Quantum entanglement distribution in 76 db attenuation is performed; we observed bell inequation symmetry broken, the result is 2.5±0.8. In quantum teleportation the transmitted state over 3:1 and the confidence over 95%, when the attenuation is 46 db. Quantum experiment control unit is stable and reliable during the experiment, satisfying the experimental requirement.