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

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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.