Experimental Set-up (IMAGE) University of Basel Caption Photon pairs are produced with a source (green point). A photon from each pair is emitted upwards; the other is directed into a semi-transparent mirror (black circle). Following the mirror, the photon exists in two entangled states (symbolized by the yellow figure of eight). The photon is then detected by a detector (top right) or by the eye of the human observer (bottom right). In order for the photons to be detectable by the human eye, they are amplified by laser beams (boxes with yellow triangle symbol). The amplitude and phase of the laser beams can be changed during each run of the experiment, with the result that either the detector or the eye can detect the light pulse, and sometimes both simultaneously or neither at all. Through statistical analysis of the perception of light, quantum physicists can then infer the existence of quantum entanglement. Credit Illustration: Valentina Caprara Vivoli Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.