Time-resolved measurement of Bell inequalities and the coincidence loophole

Abstract

We report an Einstein-Podolsky-Rosen-Bohm experiment with a pulsed source of entangled pairs of photons, recording the time of arrival of the pulses and of the detection of each single photon. This allows varying the parameters of the analysis (as the size of the time coincidence window) at will after the experiment has ended. Among other results, we present the measurement of the time variation of the Clauser-Horne-Shimony-Holt parameter during the pulse. The obtained results close (or at least impose new and tight restrictions to) the last loophole that remains open in the tests of quantum mechanics vs local realism (the so-called coincidence loophole).