Alain Aspect and his colleagues switched how they measured pairs of photons while the light was still in flight. Their experiment sharpened an existing test of quantum entanglement.
Royal Swedish Academy of SciencesPhysical Review Letters / American Physical SocietyLaboratoire Charles Fabry, Institut d’OptiqueIn 1972, Stuart Freedman and John Clauser measured correlations between pairs of photons that violated a Bell inequality. Their measurement settings stayed fixed during each run. A decade later, Aspect, Jean Dalibard and Gérard Roger switched the settings while the photons were travelling. The correlations still exceeded the bound predicted by local hidden-variable models under the assumptions of the test. Later experiments by Aspect’s team used individual photons to study interference and ultracold atoms to see how disorder can stop matter waves from spreading.
Royal Swedish Academy of SciencesPhysical Review Letters / American Physical SocietyLaboratoire Charles Fabry, Institut d’OptiqueThe work behind the recognition
Work, in context- 1982
Bell tests with changing measurement settings
With Jean Dalibard and Gérard Roger, Aspect published a Bell-inequality experiment using time-varying analyzers. The work sharpened experimental tests of entanglement and the distinction between quantum correlations and local classical explanations. It was part of a sequence of experiments, with explicit experimental limitations.
Coauthored experiment by Alain Aspect, Jean Dalibard and Gérard Roger.
Source-supported recordPhysical Review Letters / American Physical Society - 1986
Testing the behavior of a single photon
With Philippe Grangier and Gérard Roger, Aspect reported photon anticorrelation at a beam splitter and single-photon interference. The experiments connected particle-like detection with wave-like interference, making the nonclassical nature of light accessible through controlled measurements.
Coauthored experiment by Philippe Grangier, Gérard Roger and Alain Aspect.
Source-supported recordLaboratoire Charles Fabry, Institut d’Optique - 2008
Disorder as a quantum-simulation tool
Aspect coauthored the direct observation of Anderson localization of matter waves in controlled disorder. Ultracold atoms provided a deliberately engineered physical system for studying wave transport and localization, extending the experimental tools available for quantum simulation.
Alain Aspect was a coauthor of the collaborative matter-wave localization experiment; no sole experimental credit is implied.
Source-supported recordLaboratoire Charles Fabry, Institut d’Optique
Keep in perspective
The 1982 experiment addressed how the analyzer settings were chosen. Later experiments closed additional loopholes.
The evidence map
Both views link each contribution to its sources. Choose a contribution on the map or read them all in the list.
Bell tests with changing measurement settings
Experimental Test of Bell’s Inequalities Using Time-Varying Analyzers
Supports: Aspect, Dalibard and Roger authorship; time-varying analyzers and measured Bell-inequality violation.
Published 20 Dec 1982 · Checked 19 Sept 2026Credit & limits: Coauthored experiment by Alain Aspect, Jean Dalibard and Gérard Roger.
Read the full contribution| Contribution | Evidence & what it supports | Credit & limits |
|---|---|---|
| Bell tests with changing measurement settings1982 | Primary paperExperimental Test of Bell’s Inequalities Using Time-Varying Analyzers Aspect, Dalibard and Roger authorship; time-varying analyzers and measured Bell-inequality violation. Published 20 Dec 1982 · Checked 19 Sept 2026 | Coauthored experiment by Alain Aspect, Jean Dalibard and Gérard Roger. |
| Testing the behavior of a single photon1986 | Institutional recordAlain Aspect — research and selected publications Bell-test authorship and 1982 publication; 1986 single-photon experiment; 2008 Anderson-localization paper and link to quantum technologies. Checked 19 Sept 2026 | Coauthored experiment by Philippe Grangier, Gérard Roger and Alain Aspect. |
| Disorder as a quantum-simulation tool2008 | Institutional recordAlain Aspect — research and selected publications Bell-test authorship and 1982 publication; 1986 single-photon experiment; 2008 Anderson-localization paper and link to quantum technologies. Checked 19 Sept 2026 | Alain Aspect was a coauthor of the collaborative matter-wave localization experiment; no sole experimental credit is implied. |
Follow the evidence
4 sourcesPrimary papers, institutional records and attributed announcements. Each source supports the claims linked above.
- Université Paris-SaclayInstitutional record
Alain Aspect
Current Institut d’Optique professorship, Fresnel chair and emeritus CNRS role.
Checked 19 Sept 2026 - Laboratoire Charles Fabry, Institut d’OptiqueInstitutional record
Alain Aspect — research and selected publications
Bell-test authorship and 1982 publication; 1986 single-photon experiment; 2008 Anderson-localization paper and link to quantum technologies.
Checked 19 Sept 2026 - Physical Review Letters / American Physical SocietyPrimary paper
Experimental Test of Bell’s Inequalities Using Time-Varying Analyzers
Aspect, Dalibard and Roger authorship; time-varying analyzers and measured Bell-inequality violation.
Published 20 Dec 1982 · Checked 19 Sept 2026 - Royal Swedish Academy of SciencesNobel Prize background
How entanglement has become a powerful tool
Historical sequence of Bell tests and the change in analyzer settings introduced by Aspect and colleagues.
Published 4 Oct 2022 · Checked 3 Nov 2026