具有噪声存储器的量子中继器中的纠缠蒸馏与交换调度
Entanglement Distillation and Swapping Scheduling in Quantum Repeaters with Noisy Memories
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中文总结 AI 辅助
研究有噪声量子中继器网络中纠缠蒸馏与交换调度，通过分析单跳设置及蒙特卡罗模拟两跳链，明确退相干对最优操作时间的影响，如不同相干时间下各策略优劣，为大规模架构链路级原理提供见解。
中文摘要 AI 辅助
纠缠蒸馏和纠缠交换在假设量子存储器完美的情况下已被广泛研究。然而，近期量子网络将从根本上受到具有有限相干时间的量子存储器的限制，这导致这些操作的时间安排和顺序面临复杂选择。在这项工作中，我们在有噪声的量子中继器网络的基本构建模块层面研究纠缠蒸馏和纠缠交换，旨在阐明由存储器退相干引起的基本权衡。首先，我们聚焦于最小单跳设置，通过分析比较“尽快蒸馏”和“尽可能晚蒸馏”策略与简单丢弃较旧纠缠态的基线策略。我们发现，在低存储器相干时间 regime 中，丢弃较旧纠缠态可实现更高的预期输出保真度；而在高相干时间 regime 中，将蒸馏延迟到最后可实现最高的预期输出保真度，并且在大多数截止时间范围内，可实现最高的加权相干信息，但成功概率较低。然后，我们使用蒙特卡罗模拟将分析扩展到两跳中继器链。在此设置中，我们发现通过将蒸馏推迟到时间窗口结束的策略可实现最高的加权相干信息，其中“尽可能晚蒸馏然后交换”和“尽快交换然后尽可能晚蒸馏”在不同工作点领先，而“丢弃最旧然后交换”在任何测试 regime 中都从未达到正的加权相干信息。这些结果共同阐明了退相干如何重塑量子网络中的最优操作时间，并为支配更大规模架构的链路级原理提供了有启发性的见解。
英文摘要
Entanglement distillation and entanglement swapping have been extensively studied assuming perfect quantum memories. However, near-term quantum networks will be fundamentally limited by quantum memories with a finite coherence time, resulting in complex choices for the timing and ordering of these operations. In this work, we study entanglement distillation and entanglement swapping at the level of the elementary building blocks of noisy quantum repeater networks, with the goal of elucidating the fundamental tradeoffs induced by memory decoherence. First, we focus on a minimal one-hop setting, where we analytically compare ``distill-as-soon-as-possible'' and ``distill-as-late-as-possible'' strategies against a baseline strategy that simply discards the older entangled state. We find that in the low memory coherence time regime, discarding the older entangled state achieves higher expected output fidelity, while in the high coherence time regime, delaying distillation until the end achieves the highest expected output fidelity and, over most of the deadline range, the highest weighted coherent information, at the expense of a lower success probability. We then extend our analysis to two-hop repeater chains using Monte Carlo simulation. In this setting, we find that the highest weighted coherent information is achieved by strategies that defer distillation to the end of the time window, with \textsf{Distill-ALAP-then-Swap-ALAP} and \textsf{Swap-ASAP-then-Distill-ALAP} leading at different operating points, while \textsf{Discard-Oldest-then-Swap} never reaches positive weighted coherent information in any regime tested. Together, these results clarify how decoherence reshapes the optimal operation timing in quantum networks and provide instructive insights into the link-level principles that govern larger-scale architectures.
