Derkach Ivan, Usenko Vladyslav C
Department of Optics, Palacky University, 771 46 Olomouc, Czech Republic.
Entropy (Basel). 2020 Dec 31;23(1):55. doi: 10.3390/e23010055.
We address the applicability of quantum key distribution with continuous-variable coherent and squeezed states over long-distance satellite-based links, considering low Earth orbits and taking into account strong varying channel attenuation, atmospheric turbulence and finite data ensemble size effects. We obtain tight security bounds on the untrusted excess noise on the channel output, which suggest that substantial efforts aimed at setup stabilization and reduction of noise and loss are required, or the protocols can be realistically implemented over satellite links once either individual or passive collective attacks are assumed. Furthermore, splitting the satellite pass into discrete segments and extracting the key from each rather than from the overall single pass allows one to effectively improve robustness against the untrusted channel noise and establish a secure key under active collective attacks. We show that feasible amounts of optimized signal squeezing can substantially improve the applicability of the protocols allowing for lower system clock rates and aperture sizes and resulting in higher robustness against channel attenuation and noise compared to the coherent-state protocol.
我们探讨了基于连续变量相干态和压缩态的量子密钥分发在基于卫星的长距离链路中的适用性，考虑了近地轨道，并考虑了强烈变化的信道衰减、大气湍流和有限数据系综大小效应。我们获得了关于信道输出上不可信过量噪声的严格安全界限，这表明需要在设置稳定以及降低噪声和损耗方面做出大量努力，或者一旦假设为个体或被动集体攻击，这些协议就可以在卫星链路上实际实现。此外，将卫星通过过程划分为离散段，并从每个段而不是整个单次通过过程中提取密钥，能够有效提高针对不可信信道噪声的鲁棒性，并在主动集体攻击下建立安全密钥。我们表明，可行量的优化信号压缩可以显著提高协议的适用性，与相干态协议相比，允许更低的系统时钟速率和孔径尺寸，并对信道衰减和噪声具有更高的鲁棒性。
