A Notable Life In Quantum Physics

Chien-Shiung Wu was one of the pioneers of quantum mechanics and high energy physics, and was a female Chinese physicists in an era where women still made up only a tiny percentage of scientists in the field. 

If something remembers you with a speech like this, one hundred and ten years after you were born, when you have long passed away, then you did something right in life.

In 1950, Chien-Shiung Wu and her student published a coincidence experiment on entangled photon pairs that were created in electron-positron annihilation. This experiment precisely verified the prediction of quantum electrodynamics. 

Additionally, it was also the first instance of a precisely controlled quantum entangled state of spatially separated particles, although Wu did not know about this at the time. 

In 1956, Wu initiated and led the so-called Wu experiment, which discovered parity nonconservation, becoming one of the greatest experiments of the 20th century. 

As Chen Ning Yang said, Wu's experiments were well known for their precision and accuracy. Experimental precision and accuracy manifested Wu's scientific spirit, which we investigate here in some detail. 

Yu Shi, "Scientific Spirit of Chien-Shiung Wu: From Quantum Entanglement to Parity Nonconservation" arXiv:2504.16978 (May 31, 2022) (This paper is the translated transcript of the speech the author made at the International Symposium Commemorating the 110th Anniversary of the Birth of Chien-Shiung Wu, on May 31, 2022 in Chinese. The above abstract is the translation of the original abstract of the speech.)

She earned her undergraduate degree in physics (which had a thesis requirement at the time) in China in 1934, prior to the Maoist Revolution, and earned a PhD working under a professor only three years older than her who had studied under Madame Curie, and under the first female PhD in Physics in China, who earned that degree at the University of Michigan (where I also earned my graduate degree). Wu earned her PhD at the University of California at Berkley in 1940 (thirty years before my father earned his PhD at Stanford).

Wu was admitted by the University of Michigan to study at her own expense, and was financially supported by her uncle. On her way to Michigan, Wu visited Berkeley, where she was so impressed, especially by Ernest O. Lawrence’s cyclotron, that she wanted to stay in Berkeley. The cyclotron had been invented by Lawrence, so it was an ideal place for studying physics. Another important factor that influenced Wu’s decision was that she cared a lot about gender equality, and there was gender discrimination at the University of Michigan. In addition, there were a lot of Chinese students at the University of Michigan at the time, and Wu didn’t want her socializing be dominated by fellow Chinese students. So she stayed in Berkeley. Her decision reflected her devotion to physics as a woman.

She then taught at Smith (from which my sister-in-law graduated), and then Princeton, and then she worked at Columbia University as part of the Manhattan Project. 

She was highly productive (publishing more than fifty papers in the early 1950s when a huge share of U.S. women were homemakers in the Baby Boom), and her early post-war research agenda involved the verification of Fermi’s theory of β decay.

Chien-Shiung Wu served as the President of the American Physical Society from 1975 to 1976.

James W. Cronin, who won the 1980 Nobel Prize for his discovery of charge conjugation-parity (CP) nonconservation, once said, “The great discovery of Chien-Shiung Wu started the golden age of particle physics.” 

She continued to publish through at least 1980, and died in February of 1997. The author of the paper had met her.