Clauser, Aspect, and Zeilinger designed and performed experiments that tested whether some of the most counterintuitive predictions of quantum mechanics could be explained by intrinsic properties that predetermine the outcomes of possible measurements. In 1972 Clauser (now with J. F. Clauser and Associates in Walnut Creek, California) and Stuart Freedman put such local hidden-variable theories to the test by generating pairs of entangled photons and analyzing the measured polarizations of the particles. By plugging the correlations between measurements into an inequality proposed by theorist John Bell, Clauser found that the results were inconsistent with those local theories. In the early 1980s, Aspect (Université Paris–Saclay and École Polytechnique in France) and his colleagues reinforced Clauser’s findings with more robust experimental setups that closed a major loophole.