Loophole-Free Bell Inequality Test

Three independent groups (Hensen et al., using electron spins; Shalm et al.; Giustina et al.) reported loophole-free violations of a Bell inequality within months of each other in 2015, simultaneously closing both the detection-efficiency and locality/communication loopholes that had left every prior Bell test open to a local-hidden-variable escape. A 2012 paper claimed a "loophole-free" test via a different, narrower method (local precertification of photon presence) that did not close the same combination of loopholes -- a real precedent worth distinguishing, not a competing discovery date. Builds on the original Bell tests of the 1970s-80s (Freedman-Clauser, Aspect), which is Basic's pre-1976 boundary case and not itself in this dataset.