John Clauser and Stuart Freedman tested local hidden-variable theories with photons from a calcium atomic cascade. They measured joint detections behind differently oriented polarizers and compared a combination of those rates with a Bell inequality. The observed violation agreed with quantum mechanics, turning assumptions about distant outcomes into a quantitative laboratory test. The experiment used additional assumptions about detection and the sampled photon pairs; it did not close every later-identified experimental loophole.[ref]
Experimental Test of Local Hidden-Variable Theories by Stuart Jay Freedman and John Francis Clauser. 1972 paper, abstract, apparatus and inequality comparison
A physicist who performed experimental tests of Bell inequalities.[ref]
Professional profile of John Francis Clauser (johnclauser.com). Self-authored opening identity paragraph.
Portrait of John Clauser
. Peter Lyons, photograph; Adem, existing portrait crop. CC BY-SA 4.0, via Wikimedia Commons. Source. Articles by others on the same topic
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John Clauser is a prominent American physicist known for his pioneering work in the field of quantum mechanics. He is particularly celebrated for his role in experiments that test the foundations of quantum theory, including his work on Bell's theorem and the demonstration of quantum entanglement. In 1969, Clauser and his collaborators conducted one of the first experiments to test Bell's inequalities, which provided evidence for the existence of quantum entanglement.