Alain Aspect
Encyclopedia
Alain Aspect is a French
physicist
noted for his experimental work on quantum entanglement
.
Aspect is a graduate of the École Normale Supérieure de Cachan
(ENS Cachan). He passed the 'agrégation
' in physics in 1969 and received his master's degree from Université d'Orsay. He then did his national service, teaching for three years in Cameroon
.
In the early 1980s, while working on his PhD thesis from the lesser academic rank of lecturer, he performed the elusive "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 particle
s were separated by an arbitrarily large distance (see EPR paradox
). 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 the polarization
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" by Einstein (who doubted the physical reality of this effect). However, these experiments do not allow faster-than-light communication, as the events themselves appear to be 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. The 2010 Wolf Prize in physics was awarded to Aspect, Anton Zeilinger
and John Clauser
.
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
physicist
Physicist
A physicist is a scientist who studies or practices physics. Physicists study a wide range of physical phenomena in many branches of physics spanning all length scales: from sub-atomic particles of which all ordinary matter is made to the behavior of the material Universe as a whole...
noted for his experimental work on quantum entanglement
Quantum entanglement
Quantum entanglement occurs when electrons, molecules even as large as "buckyballs", photons, etc., interact physically and then become separated; the type of interaction is such that each resulting member of a pair is properly described by the same quantum mechanical description , which is...
.
Aspect is a graduate of the École Normale Supérieure de Cachan
École Normale Supérieure de Cachan
The École Normale Supérieure de Cachan is one of the most prestigious French Grandes Écoles. Like all the other Grandes Écoles, this higher education institution is not included in the mainstream framework of the French public universities...
(ENS Cachan). He passed the 'agrégation
Agrégation
In France, the agrégation is a civil service competitive examination for some positions in the public education system. The laureates are known as agrégés...
' in physics in 1969 and received his master's degree from Université d'Orsay. He then did his national service, teaching for three years in Cameroon
Cameroon
Cameroon, officially the Republic of Cameroon , is a country in west Central Africa. It is bordered by Nigeria to the west; Chad to the northeast; the Central African Republic to the east; and Equatorial Guinea, Gabon, and the Republic of the Congo to the south. Cameroon's coastline lies on the...
.
In the early 1980s, while working on his PhD thesis from the lesser academic rank of lecturer, he performed the elusive "Bell test experiments
Bell test experiments
The Bell test experiments serve to investigate the validity of the entanglement effect in quantum mechanics by using some kind of Bell inequality...
" that showed that Albert Einstein
Albert Einstein
Albert Einstein was a German-born theoretical physicist who developed the theory of general relativity, effecting a revolution in physics. For this achievement, Einstein is often regarded as the father of modern physics and one of the most prolific intellects in human history...
, Boris Podolsky
Boris Podolsky
Boris Yakovlevich Podolsky , was an American physicist of Russian Jewish descent.-Education:In 1896, Boris Podolsky was born into a poor Jewish family in Taganrog, in what was then the Russian Empire, and he moved to the United States in 1913...
and Nathan Rosen
Nathan Rosen
Nathan Rosen was an American-Israeli physicist noted for his study on the structure of the hydrogen molecule and his work with Albert Einstein and Boris Podolsky on entangled wave functions and the EPR paradox.-Background:Nathan Rosen was born into a Jewish family in Brooklyn, New York...
's reductio ad absurdum
Reductio ad absurdum
In logic, proof by contradiction is a form of proof that establishes the truth or validity of a proposition by showing that the proposition's being false would imply a contradiction...
of quantum mechanics
Quantum mechanics
Quantum mechanics, also known as quantum physics or quantum theory, is a branch of physics providing a mathematical description of much of the dual particle-like and wave-like behavior and interactions of energy and matter. It departs from classical mechanics primarily at the atomic and subatomic...
, namely that it implied 'ghostly action at a distance', did in fact appear to be realised when two particle
Elementary particle
In particle physics, an elementary particle or fundamental particle is a particle not known to have substructure; that is, it is not known to be made up of smaller particles. If an elementary particle truly has no substructure, then it is one of the basic building blocks of the universe from which...
s were separated by an arbitrarily large distance (see EPR paradox
EPR paradox
The EPR paradox is a topic in quantum physics and the philosophy of science concerning the measurement and description of microscopic systems by the methods of quantum physics...
). A correlation
Correlation
In statistics, dependence refers to any statistical relationship between two random variables or two sets of data. Correlation refers to any of a broad class of statistical relationships involving dependence....
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 the polarization
Photon polarization
Photon polarization is the quantum mechanical description of the classical polarized sinusoidal plane electromagnetic wave. Individual photons are completely polarized...
measurement of one photon
Photon
In physics, a photon is an elementary particle, the quantum of the electromagnetic interaction and the basic unit of light and all other forms of electromagnetic radiation. It is also the force carrier for the electromagnetic force...
, 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
Bell's theorem
In theoretical physics, Bell's theorem is a no-go theorem, loosely stating that:The theorem has great importance for physics and the philosophy of science, as it implies that quantum physics must necessarily violate either the principle of locality or counterfactual definiteness...
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
Principle of locality
In physics, the principle of locality states that an object is influenced directly only by its immediate surroundings. Experiments have shown that quantum mechanically entangled particles must violate either the principle of locality or the form of philosophical realism known as counterfactual...
. See local hidden variable theory
Local hidden variable theory
In quantum mechanics, a local hidden variable theory is one in which distant events are assumed to have no instantaneous effect on local ones....
.
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" by Einstein (who doubted the physical reality of this effect). However, these experiments do not allow faster-than-light communication, as the events themselves appear to be inherently random.
After his works on Bell's inequalites, he turned toward studies of laser cooling
Laser cooling
Laser cooling refers to the number of techniques in which atomic and molecular samples are cooled through the interaction with one or more laser light fields...
of neutral atoms and is now mostly involved in Bose-Einstein condensates related experiments.
Aspect was deputy director of the French "grande école
Grandes écoles
The grandes écoles of France are higher education establishments outside the main framework of the French university system. The grandes écoles select students for admission based chiefly on national ranking in competitive written and oral exams...
" SupOptique
École supérieure d'optique
The École supérieure d'optique , nicknamed "SupOptique", is the leading French grande école in the field of optics and its industrial and scientific applications, and a member of the prestigious UniverSud Paris and ParisTech...
until 1994. He is a member of the French Academy of Sciences
French Academy of Sciences
The French Academy of Sciences is a learned society, founded in 1666 by Louis XIV at the suggestion of Jean-Baptiste Colbert, to encourage and protect the spirit of French scientific research...
and French Academy of Technologies
French Academy of Technologies
The French Academy of Technologies is a learned society, founded in 2000, with an emphasis on technology. It is the newest of French academies...
, and professor at the Ecole Polytechnique
École Polytechnique
The École Polytechnique is a state-run institution of higher education and research in Palaiseau, Essonne, France, near Paris. Polytechnique is renowned for its four year undergraduate/graduate Master's program...
. In 2005 he was awarded the gold medal of the Centre national de la recherche scientifique
Centre national de la recherche scientifique
The National Center of Scientific Research is the largest governmental research organization in France and the largest fundamental science agency in Europe....
, where he is currently Research Director. The 2010 Wolf Prize in physics was awarded to Aspect, Anton Zeilinger
Anton Zeilinger
Anton Zeilinger is an Austrian quantum physicist. He is currently professor of physics at the University of Vienna, previously University of Innsbruck. He is also the director of the Vienna branch of the Institute for Quantum Optics and Quantum Information IQOQI at the Austrian Academy of Sciences...
and John Clauser
John Clauser
John Francis Clauser is an American theoretical and experimental physicist known for contributions to the foundations of quantum mechanics, in particular the Clauser-Horne-Shimony-Holt inequality....
.
Selected 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)
- 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)
- To be or not to be local, A. Aspect, Nature, Vol. 446, pp. 866–867 (2007)
External links
- Aspect's homepage
- Atom Optics group, Laboratoire Charles Fabry, Institut d'Optique
- Biography at CNRS
- http://www.lcf.institutoptique.fr/Groupes-de-recherche/Optique-atomique/Membres/Membres-permanents/Alain-Aspect
- http://www.academie-sciences.fr/academie/membre/Aspect_Alain.htm
- Lévy Statistics and Laser Cooling: http://www.cambridge.org/us/knowledge/isbn/item1169242/?site_locale=en_US
- Speakable and Unspeakable in Quantum Mechanics: http://www.cambridge.org/us/knowledge/isbn/item1149699/?site_locale=en_US
- Introduction to Quantum Optics: http://www.cambridge.org/us/knowledge/isbn/item2712310/Introduction%20to%20Quantum%20Optics/?site_locale=en_US