Alain Aspect

Alain Aspect (born 15 June 1947 in Agen) is a French physicist and alumnus of the École Normale Supérieure de Cachan in France. In the early 1980s, with collaborators in France, he performed the crucial "Bell test experiments" that showed that Albert Einstein, Boris Podolsky and Nathan Rosen's "reductio ad absurdum" of quantum mechanics, namely that it implied 'ghostly action at a distance', did in fact appear to be realised when two particles were separated by an arbitrarily large distance. A correlation between their wave functions remained, as they were once part of the same wave-function that was not disturbed before one of the child particles was measured.

If quantum theory is correct, the determination of an axis direction for polarisation measurement of one photon, forcing the wave function to 'collapse' onto that axis, will influence the measurement of its twin. This influence occurs despite any experimenters not knowing which axes have been chosen by their distant colleagues, and at distances that disallow any communication between the two photons, even at the speed of light.

Aspect's experiments were considered to provide overwhelming support to the thesis that Bell's inequalities are violated in its CHSH version. However, his results were not completely conclusive, since there were so-called loopholes that allowed for alternative explanations that comply with local realism. See local hidden variable theory.

Stated more simply, the experiment provides strong evidence that a quantum event at one location can affect an event at another location without any obvious mechanism for communication between the two locations. This has been called "spooky action at a distance". However, these experiments do not allow faster-than-light communication, as the events themselves are inherently random.

After his works on Bell's inequalites, he turned toward studies of laser cooling of neutral atoms and is now mostly involved in Bose-Einstein condensates related experiments.

Aspect was deputy director of the French "grande école" SupOptique until 1994. He is a member of the French Academy of Sciences and French Academy of Technologies, and professor at the Ecole Polytechnique. In 2005 he was awarded the gold medal of the Centre national de la recherche scientifique, where he is currently Research Director.

elected bibliography

* "Experimental Realization of Einstein-Podolsky-Rosen-Bohm Gedankenexperiment: A New Violation of Bell's Inequalities", A. Aspect, P. Grangier, and G. Roger, Physical Review Letters, Vol. 49, Iss. 2, pp.91-94 (1982) doi|10.1103/PhysRevLett.49.91
* "Experimental Test of Bell's Inequalities Using Time-Varying Analyzers", A. Aspect, J. Dalibard and G. Roger, Physical Review Letters, Vol. 49, Iss. 25, pp. 1804-1807 (1982) doi|10.1103/PhysRevLett.49.1804
* "To be or not to be local", A. Aspect, Nature, Vol. 446, pp. 866-867 (2007)

See also

* Abner Shimony
* EPR paradox

External links

* [http://atomoptic.iota.u-psud.fr/ Atom Optics group] , Laboratoire Charles Fabry, Institut d'Optique
* [http://www2.cnrs.fr/en/394.htm Biography] at CNRS


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