Alain Aspect

Alain Aspect is a French physicist whose experiments with entangled photons tested Bell inequalities and helped establish quantum nonlocal correlations experimentally.

Aspect's 1982 Bell test: A series of optical experiments by Alain Aspect’s team that tested Bell inequalities using pairs of entangled photons. This landmark experiment used rapidly switched analyzers to address a locality loophole.
Quantum entanglement: A quantum relation in which multiple systems share a state that cannot be described as independent states. Entanglement supplied the correlated photon pairs in Aspect’s tests.
Bell's theorem: A theorem showing that no theory satisfying specified locality and realism assumptions can reproduce all quantum-mechanical predictions. It explains why Aspect’s experiments could test competing accounts of quantum correlations.
John Clauser: An American physicist who performed early experimental tests of Bell inequalities using entangled photons. Clauser’s pioneering experiments preceded and influenced Aspect’s more stringent tests.
Aspect's 1981 Bell test: An experiment by Alain Aspect’s team that tested Bell’s inequality with polarization-correlated photon pairs. It established the experimental approach that the 1982 tests refined.
Photon polarization: The orientation of a photon's electromagnetic field, used as a two-outcome measurement degree of freedom. Polarization analyzers let the experiments record binary outcomes at chosen settings.
Bell inequality: A mathematical bound on correlations implied by assumptions such as locality in hidden-variable theories. The inequalities supplied the thresholds Aspect’s measured correlations were compared against.
John Bell: A physicist whose theorem showed that local hidden-variable theories obey limits on quantum correlations. Bell supplied the theoretical test that Aspect’s experiments implemented.
Clauser–Horne–Shimony–Holt inequality: A Bell inequality that bounds correlations predicted by local hidden-variable theories. Aspect’s photon experiments tested this inequality against quantum predictions.
Polarization analyzer: An optical device that separates or measures light according to its polarization. Aspect’s analyzers converted photon polarization into countable detector outcomes.

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