Experimental Quantum Physics

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A violation of Bell's inequality performed live


A loophole-free test of Bell's inequality provides a strong statement about the description of nature on the fundamental level but requires very involved experimental techniques and could be successfully conducted only recently. Besides performing such a conclusive experiment, our goal also was to show to the interested audience how it is performed. Therefore, we have set up a web server providing real-time access to the collected data and other relevant information.

After performing preparatory calibration measurements, on 14.06.2016 we have started an attempt with the goal of obtaining a defined number of measurement events. This number (5000 for each of the two prepared entangled atomic states) should be sufficient to provide a significant violation. The run took overall 10 days including daily maintenance stops. The resulting S-parameters are 2.139 ± 0.048 and 2.055 ± 0.048, respectively, providing the first loophole-free violation of Bell's inequality with all relevant data publicly accessible during the whole course of the experiment.