John Clauser
John Clauser in 2016
John Francis Clauser

(1942-12-01) December 1, 1942 (age 81)
Alma mater
Known forBell test experiments, CHSH inequality
Scientific career
FieldsFoundation of quantum mechanics
ThesisMeasurement of the Cosmic Microwave Background by Optical Observations of Interstellar Molecules (1970)
Doctoral advisorPatrick Thaddeus

John Francis Clauser (/ˈklzər/; born December 1, 1942) is an American theoretical and experimental physicist known for contributions to the foundations of quantum mechanics, in particular the Clauser–Horne–Shimony–Holt inequality.[1] Clauser was awarded the 2022 Nobel Prize in Physics, jointly with Alain Aspect and Anton Zeilinger "for experiments with entangled photons, establishing the violation of Bell inequalities and pioneering quantum information science".[2]


Clauser was born in Pasadena, California. His father, Francis H. Clauser, was a professor of aeronautical engineering who founded and chaired the aeronautics department at Johns Hopkins University. He later served as the Clark Blanchard Millikan Professor of Engineering at the California Institute of Technology (Caltech).[3] His mother, Catharine McMillan, was the humanities librarian at Caltech and sister of 1951 Nobel Prize in Chemistry laureate Edwin McMillan.[4]

He received a bachelor of science in physics from Caltech in 1964, where he was a member of Dabney House.[5] He received a master of arts in physics in 1966 and a doctor of philosophy in physics in 1969 from Columbia University[1] under the direction of Patrick Thaddeus.[6][7]

From 1969 to 1975, he worked as a postdoctoral researcher at the University of California, Berkeley and Lawrence Berkeley National Laboratory. In 1972, working with Berkeley graduate student Stuart Freedman, he carried out the first experimental test of the CHSH-Bell's theorem predictions. This was the first experimental observation of a violation of a Bell inequality.[1][8] In 1974, working with Michael Horne, he first showed that a generalization of Bell's Theorem provides severe constraints for all local realistic theories of nature (a.k.a. objective local theories). That work introduced the Clauser–Horne (CH) inequality as the first fully general experimental requirement set by local realism. It also introduced the "CH no-enhancement assumption", whereupon the CH inequality reduces to the CHSH inequality, and whereupon associated experimental tests also constrain local realism. Also in 1974 he made the first observation of sub-Poissonian statistics for light (via a violation of the Cauchy–Schwarz inequality for classical electromagnetic fields), and thereby, for the first time, demonstrated an unambiguous particle-like character for photons.

Clauser worked as a research physicist mainly at Lawrence Livermore and Berkeley from 1975 to 1997. In 1976 he carried out the world's second experimental test of the CHSH-Bell's Theorem predictions.[9]

Clauser was awarded the Wolf Prize in Physics in 2010 together with Alain Aspect and Anton Zeilinger. The three were also jointly awarded the 2022 Nobel Prize in Physics.[10]

Climate change denial

In May 2023, Clauser joined the board of the CO2 Coalition, a climate change denial organization.[11]

In November 2023, Clauser called himself a "climate denier" at an event organized by the Deposit of Faith Coalition, a group of Catholic organizations.[12] He believes that Earth's temperature is primarily determined by cloud cover instead of, as stated by the scientific consensus on climate change,[13] carbon dioxide emissions. He has concluded that clouds have a net cooling effect on the planet, and stated "there is no climate crisis."[12] The consensus among meteorologists and climatologists is that low-altitude, thick clouds do have a net cooling effect, but high-altitude, thin ones have a warming effect;[14] there is observational evidence that the overall current cloud feedback amplifies global warming, and does not have a cooling effect.[15]

See also


  1. ^ a b c "John F. Clauser". American Institute of Physics.
  2. ^ "The Nobel Prize in Physics 2022". The Royal Swedish Academy of Sciences (Press release). October 4, 2022.
  3. ^ "Proving that Quantum Entanglement is Real". California Institute of Technology. September 20, 2022. Retrieved October 6, 2022.
  4. ^ "Caltech Alum Wins Nobel Prize in Physics". California Institute of Technology. October 4, 2022. Retrieved October 6, 2022.
  5. ^ The Big T. Associated Students of the California Institute of Technology. 1963.
  6. ^ Clauser, John F. (1970). Measurement of the Cosmic Microwave Background by Optical Observations of Interstellar Molecules (Ph.D. thesis). Columbia University. OCLC 145659. ProQuest 302516464.
  7. ^ "Patrick Thaddeus (1932–2017)" (PDF). Biographical Memoirs. National Academy of Sciences. p. 12.
  8. ^ Freedman, Stuart J.; Clauser, John F. (April 3, 1972). "Experimental Test of Local Hidden-Variable Theories". Physical Review Letters. 28 (14): 938-941. Bibcode:1972PhRvL..28..938F. doi:10.1103/PhysRevLett.28.938. Retrieved October 5, 2022.
  9. ^ "Proving that Quantum Entanglement is Real". California Institute of Technology. September 20, 2022. Retrieved October 6, 2022.
  10. ^ "The Nobel Prize in Physics 2022". Retrieved October 4, 2022.
  11. ^ Cho, Seunghan (June 26, 2023). "노벨물리학상 수상자 "정치인들, 잘못된 과학정보 만들어내"" [Nobel laureate in physics "Politicians create false scientific information"]. The Korea Economic Daily (in Korean). Yonhap News Agency. Retrieved July 28, 2023.
  12. ^ a b Joselow, Maxine (November 16, 2023). "He won a Nobel Prize. Then he started denying climate change". Washington Post. ISSN 0190-8286. Archived from the original on November 18, 2023. Retrieved November 17, 2023.
  13. ^ Oreskes, Naomi (December 3, 2004). "The Scientific Consensus on Climate Change". Science. 306 (5702): 1686. doi:10.1126/science.1103618.
  14. ^ Graham, Steve (March 1, 1999). "Clouds & Radiation". NASA Earth Observatory. Archived from the original on November 19, 2023. Retrieved November 19, 2023.
  15. ^ Held, Isaac M. (July 19, 2021). "Observational evidence that cloud feedback amplifies global warming". PNAS. 118 (30). doi:10.1073/pnas.2026290118. PMC 8325336.