 | Alain Aspect, John F. Clauser, and Anton Zeilinger have been awarded the 2022 Nobel Prize in Physics for their work on demonstrating the violation of Bell inequalities, research that has proved foundational for quantum information science, the Royal Swedish Academy of Sciences announced on Tuesday.
Clauser, now of J. F. Clauser & Associates in Walnut Creek, California, formulated and performed the first practical experiment to test whether quantum mechanics is complete or there are local hidden variables—the question at the core of Bell's inequality. In 1972 he and Stuart Freedman built a setup that sent two entangled photons in opposite directions toward fixed polarization filters. Depending on the angles of the filters and the polarization of the photons, the photons either were blocked or passed through and pinged a detector. The measured coincidence rate for two given polarizer angles agreed with the predictions of quantum mechanics but not with any classical formulation: It violated Bell's inequality.
But the experimental limitations, such as the polarizers' fixed positions, left loopholes and therefore doubts. Aspect (Université Paris–Saclay and École Polytechnique, France) created improved versions of Clauser's experiment. First, he added the ability to register the photons that were blocked by the filters. And in 1982, he added a method to select one of two filters at different angles for each photon in a few billionths of a second, too little time for information about the filter to reach and influence the other side of the experiment. The measurement once again confirmed quantum mechanics and closed an important loophole.
Zeilinger (University of Vienna, Austria) was the first to demonstrate quantum teleportation—a phenomenon in which quantum information is transferred from one particle in an entangled pair to a third particle. That 1997 work was followed up the next year with the successful entanglement of two particles that never directly interact through a trick known as entanglement swapping. Two pairs of photons have one partner from each pair entangled, and thus the other partners are also entangled despite never being in contact.
The awardees will share the 10 million Swedish krona (roughly $900 000) prize.
This article will be updated later today.
SELECTED ARTICLES IN PHYSICS TODAY - N. D. Mermin, Is the Moon there when nobody looks? Reality and the quantum theory. April 1985, page 38.
- C. H. Bennett, Quantum information and computation. October 1995, page 24.
- G. P. Collins, Quantum teleportation channels opened in Rome and Innsbruck. February 1998, page 18.
- R. A. Bertlmann, Magic moments with John Bell. July 2015, page 40.
- J. L. Miller, Three groups close the loopholes in tests of Bell's theorem. January 2016, page 14.
- A. G. Smart, Quantum entanglement reaches new heights. August 2017, page 14.
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