We perform a numerical study of the distribution of entanglement on a real-world fiber grid connecting the German cities of Bonn and Berlin. The connection is realized using a chain of processing-node quantum repeaters spanning roughly 900 kilometers. Their placement is constrained by the fiber grid we consider, resulting in asymmetric links. We investigate how minimal hardware requirements depend on the target application, as well as on the number of repeaters in the chain. We find that requirements for blind quantum computing are markedly different than those for quantum key distribution, with the required coherence time being around two and a half times larger for the former. Further, we observe a trade-off regarding how target secret-key rates are achieved when using different numbers of repeaters: comparatively low-quality entangled states generated at a high rate are preferred for higher numbers of repeaters, whereas comparatively high-quality states generated at a lower rate are favored for lower numbers of repeaters. To obtain our results we employ an extensive simulation framework implemented using NetSquid, a discrete-event simulator for quantum networks. These are combined with an optimization methodology based on genetic algorithms to determine minimal hardware requirements.

中文翻译：

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将可信节点升级到超过 900 km 光纤的中继器链的要求


我们对连接德国波恩和柏林的现实世界光纤网格上的纠缠分布进行了数值研究。该连接是通过一条横跨约 900 公里的处理节点量子中继器链实现的。它们的放置受到我们考虑的光纤网格的限制，从而导致不对称链路。我们研究了最低硬件要求如何取决于目标应用以及链中中继器的数量。我们发现盲量子计算的要求与量子密钥分发的要求明显不同，所需的相干时间大约是前者的两倍半。此外，我们观察到在使用不同数量的中继器时如何实现目标密钥速率的权衡：以高速率生成的相对低质量的纠缠态对于更多数量的中继器来说是首选，而生成相对高质量的状态较低的速率受到较少数量的中继者的青睐。为了获得结果，我们采用了使用 NetSquid（量子网络的离散事件模拟器）实现的广泛模拟框架。这些与基于遗传算法的优化方法相结合，以确定最低的硬件要求。