We develop new methods of quantifying the impact of photon detector imperfections on achievable secret key rates in Time-Entanglement based Quantum Key Distribution (QKD). We address photon detection timing jitter, detector downtime, and photon dark counts and show how each may decrease the maximum achievable secret key rate in different ways. We begin with a standard Discrete Memoryless Channel (DMC) model to get a good bound on the mutual information lost due to the timing jitter, then introduce a novel Markov Chain (MC) based model to characterize the effect of detector downtime and show how it introduces memory to the key generation process. Finally, we propose a new method of including dark counts in the analysis that shows how dark counts can be especially detrimental when using the common Pulse Position Modulation (PPM) for key generation. Our results show that these three imperfections can significantly reduce the achievable secret key rate when using PPM for QKD. Additionally, one of our main results is providing tooling for experimentalists to predict their systems' achievable secret key rate given the detector specifications.
翻译:我们开发了新的方法来量化光子探测器的不完善对基于时联的量子键分布(QKD)中可实现的秘密密钥率的影响。 我们处理光子探测器时间感应、检测或故障时间和光子暗计数,并展示每种方法如何以不同方式降低最大可实现的秘密密钥率。 我们从标准的分辨无内聚性通道(DMC)模型开始,以对由于时间偏移而丢失的相互信息进行良好的约束, 然后引入一个基于新颖的马克夫链(MC)模型, 以描述探测器下调时间的效果, 并展示它是如何将内存引入关键生成过程的。 最后, 我们提出一种新的方法, 将暗计数纳入分析, 以显示在使用通用 Pulse 定位变速器( PPPM) 进行关键生成时, 暗计数会如何特别有害。 我们的结果表明, 这三个不完善的模型可以大大降低在QKD中使用 PPM时的密钥率。 此外, 我们的主要结果之一是为实验家提供工具, 以预测其系统的可实现的密钥率, 。