Connection-less, packet-switched quantum network architectures distribute entanglement across multi-hop paths through sequential entanglement swapping, in which each node acts on purely local state information. The architectural advantages over the connection-oriented alternative -- simultaneous SWAP-ASAP -- are compelling, but sequential swapping holds partial chains in intermediate buffers between successive swaps, exposing them to memory decoherence in a way simultaneous SWAP-ASAP avoids by design. We present a proof-of-principle study at fixed chain length $n = 4$ in which each elementary link is governed by a fixed reinforcement-learning policy optimizing the secret-key rate of the six-state protocol, leaving the network-layer protocol as the sole independent variable. Sweeping the network-layer memory coherence time $T_c^{\mathrm{ext}}$ over four orders of magnitude reveals a clear regime structure governed by the dimensionless ratio $T_c^{\mathrm{ext}}/τ$, where $τ$ is the per-link entanglement heralding latency. Simultaneous SWAP-ASAP delivers a constant rate across the full sweep. Sequential swapping, by contrast, collapses to zero end-to-end deliveries below $T_c^{\mathrm{ext}}/τ= 25$, and begins recovering at $T_c^{\mathrm{ext}}/τ= 50$. It remains limited by the simultaneous rate, which it saturates only at the relaxed end of the sweep. These results suggest that the connection-less penalty is a near-term phenomenon tied to present-day memory coherence rather than a fundamental property of sequential swapping.

翻译：无连接、分组交换的量子网络架构通过顺序式纠缠交换在多跳路径上分发纠缠，其中每个节点仅依据本地状态信息执行操作。与面向连接的替代方案——同时式SWAP-ASAP相比，该架构具有显著优势，但顺序式交换会在中间缓冲区中保留部分链，并在后续交换之间暴露于退相干过程，而同时式SWAP-ASAP通过设计规避了这一问题。我们针对固定链长$n=4$开展原理性验证研究，其中每个基本链路受固定强化学习策略控制，该策略优化六态协议的密钥生成率，将网络层协议作为唯一的独立变量。通过将网络层存储相干时间$T_c^{\mathrm{ext}}$跨越四个数量级扫描，揭示了由无量纲比值$T_c^{\mathrm{ext}}/τ$决定的清晰相结构，其中$τ$为每链路纠缠确认延迟。同时式SWAP-ASAP在全扫描范围内提供恒定速率。相比之下，顺序式交换在$T_c^{\mathrm{ext}}/τ<25$时端到端交付率降至零，并在$T_c^{\mathrm{ext}}/τ=50$时开始恢复。其性能始终受限于同时式方案速率，仅在扫描的宽松端达到饱和。这些结果表明，无连接方式的性能惩罚并非顺序式交换的基本属性，而是与当今存储相干性相关的短期现象。