Clarifications on the Chien-Shiung Wu feature

“Chien-Shiung Wu’s trailblazing experiments in particle physics ” by Chon-Fai Kam, Cheng-Ning Zhang, and Da Hsuan Feng (Physics Today, December 2024, page 28) helps to correct the scientific community’s failure to give appropriately enormous credit to Wu for her many accomplishments, especially her leadership of what may well be described as the most important experiment in the history of particle physics: the demonstration that the weak interaction violates parity conservation. The article’s brief mention of the test of hidden-variable theories, however, needs more complete referencing.

Following John Bell’s celebrated 1964 work in which he derived an inequality that must be satisfied by local hidden-variable theories, it was a paper by John Clauser, Michael Horne, Abner Shimony, and Richard Holt that proposed a practicable experiment that could test the Bell inequalities. ¹ As a postdoc at the University of California, Berkeley, Clauser brought that idea to Stuart Freedman, who was then a UC Berkeley graduate student under the guidance of Eugene Commins. It was Freedman who conducted the experiment as his thesis, and the work was published in Physical Review Letters in 1972. ² The experiment provided compelling evidence that local hidden-variable theories were wrong.

As Kam, Zhang, and Feng note in their article, Alain Aspect, Clauser, and Anton Zeilinger received the 2022 Nobel Prize in Physics “for experiments with entangled photons, establishing the violation of Bell inequalities and pioneering quantum information science.” (For additional information, see Physics Today, December 2022, page 14 .) Just as Wu died without receiving a Nobel Prize for her early photon entanglement experiment, Bell and Freedman died without receiving a Nobel Prize for their work whose significance was indicated by the awarding of the prize to Aspect, Clauser, and Zeilinger.