John Clauser

John Clauser is an American experimental and theoretical physicist known for his contributions to the foundations of quantum mechanics, particularly for the Clauser-Horne-Shimony-Holt (CHSH) inequality, the first experimental proof of non-local quantum entanglement, and the formulation of the theory of Local Realism (Clauser-Horne). Since 1997, Clauser has been a research physicist, consultant, and inventor at J.F. Clauser & Assoc. in Walnut Creek, California. In 2022, Clauser was awarded the Nobel Prize in Physics for his work on quantum entangled states.

Clauser was born on December 1st, 1942, in Pasadena, California. He attended the California Institute of Technology, graduating in 1964 with a B.S. in physics before moving to Columbia University. In 1966 he completed an M.A. in physics followed by a Ph.D. in 1969. From 1969 to 1996, Clauser worked at Lawrence Berkeley National Laboratory, Lawrence Livermore National Laboratory, and the University of California, Berkeley. In 1969, working with Michael Horne, Abner Shimony, and Richard Holt, Clauser proposed the first test of local hidden variable theories, inspired by the theoretical results of John Bell. The team provided the first experimental evidence for CHSH-Bell theorem or the CHSH inequality. In 1972, working with Stuart Freedman, Clauser performed the first experimental test of the CHSH inequality's prediction. This marks the first observation of non-local quantum entanglement and was the first experimental observation of a violation of a Bell inequality.

On October 4th, 2022, the Royal Swedish Academy of Sciences announced the 2022 Nobel prize in physics was awarded to John Clauser, Alain Aspect, and Anton Zeilinger for:

experiments with entangled photons, establishing the violation of Bell inequalities and pioneering quantum information science

The three scientists had independently:

conducted groundbreaking experiments using entangled quantum states, where two particles behave like a single unit even when they are separated. Their results have cleared the way for new technology based upon quantum information.

During the development of quantum mechanics, scientists questioned whether the correlation between entangled particles was the result of hidden variables. In the 1960s, John Stewart Bell developed the mathematical inequality, named the Bell inequality, based on this question. It states that if hidden variables cause quantum entanglement, then the results of a large number of measurements will never exceed a certain value. Experimental evidence could violate this inequality by measuring a stronger correlation than would otherwise be possible. Clauser's research developed Bell's ideas and led to a practical experiment that supported the quantum mechanical interpretation (no hidden variables) by violating a Bell inequality.