AI 中文总结
该研究针对城域量子网络互连需求，分析电信C波段纠缠光子源的时间稳定性，实验实现了城域部署下两源的可靠同步，为城市规模量子网络构建提供了实验支撑。
AI 中文摘要
时间同步是基于纠缠的量子网络的基本要求，其中光子在时域中的不可区分性对于实现Hong-Ou-Mandel干涉和纠缠交换至关重要。除了精确的时间对齐外，确保参考时钟随时间的稳定性同样关键，因为即使微小的波动也会降低网络的整体性能。本研究针对基于电信C波段工作的纠缠光子源的纠缠分发，研究其时钟同步的稳定性。利用带时间标记的符合测量分析光子探测事件之间的时间相关性，从而提取同步峰值及其长期稳定性。实验结果表明，一旦锁定，这些源在8小时的采集周期内表现出稳定的时间相关性，观测到的最大漂移约为120 ps，主要与长光纤链路相关。相关峰值的宽度与探测器抖动一致，表明系统诱导的时间展宽可忽略不计。本研究的核心结果是在实际城域部署中实现两个纠缠光子源的实验同步，其中纠缠分发通过现有电信基础设施进行，该基础设施具有不可忽略的损耗和背景噪声。在这种场景下，尽管城域光纤网络引入了显著的缺陷，但观测到的相关性仍清晰可检测，且始终能被高斯统计很好地近似。这证实这两个源不仅能在受控实验室条件下可靠同步，也能在实际操作约束下可靠同步。
英文摘要
Time synchronization is a fundamental requirement in entanglement-based quantum networks, where the indistinguishability of photons in the time domain is essential for enabling Hong-Ou-Mandel interference and entanglement swapping. In addition to precise temporal alignment, it is equally crucial to ensure the stability of the reference clock over time, as even small fluctuations can degrade the overall performance of the network. In this work, we investigate the stability of clock synchronization for entanglement distribution based on entangled-photon sources operating in the telecommunication C-band. Temporal correlations between photon detection events are analyzed using time-tagged coincidence measurements, enabling the extraction of synchronization peaks and their long-term stability. Experimental results demonstrate that, once locked, the sources exhibit stable temporal correlations over an 8-hour acquisition period, with a maximum observed drift of approximately 120 ps, primarily associated with long fiber links. The width of the correlation peak remains consistent with detector jitter, indicating negligible additional system-induced temporal broadening. A central result of this work is the experimental synchronization between two entanglement-photon sources in a realistic metropolitan deployment, where entanglement distribution is performed over existing telecommunication infrastructure characterized by non-negligible losses and background noise. In this scenario, despite the presence of significant imperfections introduced by the metropolitan-scale fiber network, the observed correlations remain clearly detectable and are consistently well-approximated by Gaussian statistics. This confirms that the two sources can be reliably synchronized not only in controlled laboratory conditions but also under real-world operating constraints.
CommentsAccepted manuscript for publication in IEEE QCE26. This work has been funded by the European Union under Horizon Europe ERC-CoG grant QNattyNet ("Quantum-Native Communication Networks: from Quantum Message to Quantum Functioning"), n.101169850. Details at https://qnattynet.quantuminternet.it
