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Performance On The Discrete Variable Based Satellite-to-Ground Quantum Key Distribution Links

This paper focuses on evaluating the available secure key lengths of the satellite-to-ground quantum key distribution (QKD) systems under multiple scenarios. The finite-length secure key rate calculation models are provided for the BB84 and BBM92 based systems, respectively, considering the practical optical link loss. The considered scenarios consist of the solar synchronous orbit satellite scenarios and the walker satellite constellation scenarios. For the BB84 protocol based QKD systems, it is shown that the amount of the secure key reduces slowly as the orbit height grows from 200km to 1100km. Increasing the size of the telescope improves the performance considerably when the deviation of the pointing error is small. However, if the pointing error becomes larger, the benefit from enlarging the telescope size shrinks heavily. On the contrary, the BBM92 protocol based QKD systems are much sensitive to the orbit height and gains much lower performance under the same configurations compared with those under the BB84 protocol. Moreover, the ground station located at higher latitude can achieve better performance than that at lower latitude in the walker satellite constellation with vertical orbital inclination.