严格时空约束下无后选择漏洞的贝尔测试
Postselection-loophole-free Bell test under strict spacetime constraints
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中文总结 AI 辅助
本文演示了同时关闭三类漏洞的光纤时间-bin纠缠贝尔测试平台，测得CHSH违反值远超定域实在论边界，为设备无关量子通信提供可行方案。
中文摘要 AI 辅助
纠缠会产生远距离量子系统之间无法用定域实在论解释的关联，贝尔不等式违反是揭示这些关联并认证非定域性的直接方式，尤其是在相关实验漏洞被关闭时。时间-bin编码是将量子信息编码为明确定义的时间模式，是光纤中分发光子纠缠的常用平台。然而，基于时间-bin纠缠的无漏洞贝尔测试受到的关注相对较少，部分原因是传统干涉测量引入的后选择漏洞。本文展示了一种基于光纤的时间-bin纠缠贝尔测试平台，同时关闭了定域性、选择自由度和后选择漏洞。我们观测到CHSH违反值为$S=2.583 \pm 0.002$，超过定域实在论边界超过265个标准差。值得注意的是，这种严格的非定域性认证是在分离距离为$49.0 \pm 0.7$米时实现的，远短于之前满足可比时空约束的光子贝尔测试。除了基础意义外，我们的结果表明时间-bin纠缠是实现实用设备无关量子通信和未来量子互联网的可行途径。
英文摘要
Entanglement gives rise to correlations between distant quantum systems that cannot be explained by local realistic theories. Bell inequality violations provide a direct way to reveal these correlations and certify nonlocality, especially when the relevant experimental loopholes are closed. Time-bin encoding, in which quantum information is encoded into well-defined temporal modes, is a commonly used platform for distributing photonic entanglement in optical fibers. Yet loophole-free Bell tests with time-bin entanglement have received comparatively little attention, owing in part to the postselection loophole introduced by conventional interferometric measurements. Here, we demonstrate a fiber-based platform for Bell tests with time-bin entanglement that simultaneously closes the locality, freedom-of-choice, and postselection loopholes. We observe a CHSH violation of $S=2.583 \pm 0.002$, exceeding the local-realistic bound by over 265 standard deviations. Notably, this rigorous certification of nonlocality is achieved at a separation distance of $49.0 \pm 0.7$ m, substantially shorter than previous photonic Bell tests addressing comparable space-time constraints. Beyond its foundational significance, our results demonstrate time-bin entanglement as a viable route towards practical device-independent quantum communication and a future quantum internet.
