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Clauser and Quantum Entanglement

John Francis Clauser, an American theoretical and experimental physicist, recently won the Nobel Prize in physics for groundbreaking work. His experiments with light helped to prove critical aspects of quantum mechanics. Clauser’s journey to discovery, however, was not at all straightforward, and very interesting indeed.

In the 1960s, in the Columbia University library, John Clauser found an inspiring article that would shape his career and lead him to pursue quantum entanglement. Quantum entanglement is a rather counterintuitive and bizarre phenomenon that explains how two subatomic particles link up in a certain way and remain linked to one another even if separated by billions of light-years of space.

Scientists including Albert Einstein and Erwin Schrödinger first discovered this phenomenon in the 1930s but were wary. The possibility of quantum entanglement was rejected by Einstein and all of his colleagues due to its lack of an “element of reality.” Einstein, along with others, argued that “hidden variables,” unaccounted-for elements of reality, should be added to quantum mechanics to explain entanglement. John Stewart Bell, an Irish physicist and author of the inspirational article, argued that it was possible to experimentally test whether quantum mechanics failed in describing these “hidden variables” with the use of local variables, which could only affect the physical setup in their immediate vicinity.

In 1972, John Clauser finally got a chance to test Bell’s proposal while in a postdoctoral position at Lawrence Berkeley National Laboratory in California in cahoots with doctoral student Stuart Freedman. Clauser and Freedman managed to create entangled photons by manipulating calcium atoms and the photons flew into polarizing filters that the scientists could rotate relative to each other. Clauser’s and Freedman’s experiments supported the theory of quantum entanglement, simultaneously paving the way for elaborate technologies that use it.

As the Nobel Prize website dictates, Clauser won his award “for experiments with entangled photons, establishing the violation of Bell inequalities and pioneering quantum information science” in 2022, and his work will be greatly beneficial for future discoveries.


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