为了应对灰霾对星地量子通信信道所带来的突发性干扰,根据灰霾天气下量子信号在自由空间中的衰减指数,本文提出了一种基于信号功率衰减最低的最优链路量子卫星切换策略。当目前的星地链路参数满足切换条件时,地面用户通过对不同信道中量子信号功率衰减系数的比对,测试到最小衰减卫星链路,基于对光子态Bell基的测量,完成卫星间的量子纠缠交换,建立新的纠缠信道,保证通信在切换过程中的连续性。仿真结果表明,当系统呼损率为5％,能见度为1 km,地面用户数分别为50、100、300,轨道高度为300 km和1400 km时,量子卫星的切换成功率分别为95％、936％、918％和92％、90％、87％。由此可见,本策略能够在保证通信可靠性的前提下,实现星地间量子信道的平稳切换,提高量子卫星通信系统在灰霾背景下链路的有效性。

In order to deal with the sudden interference of haze on quantum satellite communication channel, according to the inhomogeneity of the vertical distribution of the atmosphere, the haze aerosol particles distribution function and its chemical extinction should be analyzed, we conclude the attenuation index of quantum signal under the background of haze, and then, in this paper, according to the quantum signal attenuation index of haze in the free space, we propose an optimal link quantum satellite switching strategy based on the lowest quantum signal power attenuation. Ground station constantly testing the attenuation coefficient of quantum signal energy on different quantum channel, and periodic feedback to the quantum satellite system, as soon as the current satellite-ground communication link parameters can not be maintained or unable to satisfy the quality of communication, quantum satellite system issued the switching instruction, at this moment, the ground station compare with the attenuation coefficient of the quantum signal energy in different channels, discover the minimum attenuation satellite link, complete quantum entanglement swapping between satellites through measurement of photon state Bell-state, thus,we establish a new entanglement channel to ensure communication process continuity. Simulation results show that, if the rate of the system call loss is 5%, and the visibility is 1km,and the ground users were 50,100, 300, the success rate of quantum satellite handover on different orbital altitude of 300 km and 1400 km will be 95%, 93.6%, 91.8% and 92%, 90%, 87%.Thus, this strategy can ensuring the reliability of communication to achieve a smooth handover between satellite and ground quantum channel, enhance the effectiveness of quantum satellite communication system under the background of haze.