Automated free-space links for a three-photon test of locality in quantum mechanics

量子力学是我们对自然界最好的物理理论，但它的预测与我们的日常经验完全不同。一种这样的预测是量子非定域性，在这种情况下，量子系统上的测量显示出的相关性太强，无法用任何常识局域理论来描述。这项提议描述了一项雄心勃勃的实验，以测量3个纠缠光子之间的相关性，该实验可以区分量子力学预测和最多允许两两非局域性的一大类非局域模型。这种测试最重要、最具挑战性的方面之一是堵住所谓的地方性漏洞。这需要在最后可能的时刻将光子发送得很远，并随机选择测量设置，以便以光速传播的任何影响都不会影响测量结果。这里描述的研究计划结合了两个小组的技术专长；Resch教授的小组是纠缠光子产生和快速光开关方面的专家，而Jennewein教授的小组在量子随机数发生器和高速电子学方面拥有相当多的专业知识。我们将利用参数下转换产生高度纠缠的3光子态，利用高效、自动化的望远镜分裂并将光子发送到600米的自由空间链路上。在接收器端，高速量子随机数发生器将触发快速光学开关，在最后一刻设置测量，确保测量真正分开和独立。探测系统将记录光子点击并记录它们到达的时间。这些测量中关联的强度将允许对某些非局域自然模型进行最终的量子力学测试。我们正在申请资金，用于自动化、高效和稳定的望远镜连接，以在长距离和长时间内保持低损耗的光学连接。这项研究将对我们理解自然产生根本性的影响，并构成量子隐形传态和通信的新试验台。该项目将支持对从本科生到博士后研究员的一大批HQP进行世界级的培训。

Quantum mechanics is our best physical theory of nature yet it's predictions are completely at odds with our everyday experience. One such prediction is that of quantum nonlocality where the correlations exhibited by measurements on quantum systems are far too strong to be described by any commonsense local theory. This proposal describes an ambitious experiment to measure the correlations between 3 entangled photons which can distinguish quantum mechanical predictions against a wide class of non-local models which allow at most pairwise nonlocality. One of the most important, and challenging aspects of such a test is to close the so-called locality loophole. This requires that the photons are sent far apart and measurement settings are selected randomly at the last possible moment so that no influence traveling at the speed of light could affect the measured outcomes. The research plan described here combines the technical expertise of two groups; Prof. Resch's group are experts in entangled photon generation and fast optical switching while Prof. Jennewein's group has considerable expertise in quantum random number generators and high-speed electronics. We will produce highly entangled 3-photon states using parametric down-conversion, split up and send the photons over 600m free-space links using high-efficiency, automated telescopes. At the receivers, high-speed quantum random number generators will trigger fast optical switches to set measurements at the last moment, ensuring that the measurements are truly separate and independent. A detection system will register photon clicks and record their time of arrival. The strength of the correlations in these measurements will allow a definitive test of quantum mechanics against certain non-local models of nature. We are requesting funding for automated, high-efficiency, and stable telescope links needed to maintain a low loss optical connection over long distances and long periods of time. This research will have fundamental impact in our understanding of nature and constitute a new testbed for quantum teleportation and communication. This project will support world-class training of a large team of HQP ranging from undergraduate students to post-doctoral fellows.