Berkeley Wu and Dong Ruo-Fen arrived in
San Francisco, where Wu's plans for graduate study changed after visiting the
University of California, Berkeley. Wu missed Chinese cuisine and was not impressed with the food at Berkeley, so she always dined with friends such as Schaeffer at her favorite restaurant, the Tea Garden. Wu and her friends would get free meals that were not part of the menu due to her friendship with the owner. Wu applied for a scholarship at the end of her first year, but there was prejudice against Asian students from the department head Birge, and Wu and Yuan were instead offered a readership with a lower stipend. Yuan then applied for, and secured, a scholarship at
Caltech. Birge, however, respected Wu for her talents and was the reason Wu could enroll even though the academic year already started. Wu made rapid progress in her education and her research. Although Lawrence was officially her supervisor, she also worked closely with the famous Italian physicist
Emilio Segrè. She quickly became his favorite student and the two conducted studies on beta decay, including xenon, which would provide important results in the future of nuclear bombs. According to Segrè, Wu was a popular student who was talented. In his autobiography, Nobel laureate
Luis Alvarez said of Wu, I got to know this graduate student in this idle time. She used the same room next door, and was called "Gee Gee" [Wu's nickname at Berkeley]. She was the most talented and most beautiful experimental physicist I have ever met. Segrè recognized Wu's brilliance and compared her to Wu's heroine
Marie Curie, whom Wu always quoted, but said that Wu was more "worldly, elegant, and witty." Meanwhile, Lawrence described Wu as "the most talented female experimental physicist he had ever known, and that she would make any laboratory shine." When it came time to present her thesis in 1940, it had two separate parts presented in very neat fashion. The first was on
bremsstrahlung, the
electromagnetic radiation produced by the
deceleration of a charged particle when deflected by another charged particle, typically an
electron by an
atomic nucleus, with the latter being on radioactive Xe. She investigated the first study using beta-emitting
phosphorus-32, a radioactive isotope easily produced in the cyclotron that Lawrence and his brother
John H. Lawrence were evaluating for use in cancer treatment and as a
radioactive tracer. This marked Wu's first work with
beta decay, a subject on which she would become an authority. The second part of the thesis was about the production of radioactive isotopes of Xe produced by the
nuclear fission of
uranium with the 37-inch and 60-inch cyclotrons at the
Radiation Laboratory. Her second part on Xe and nuclear fission so impressed her committee, which featured Lawrence and
J. Robert Oppenheimer, whom Wu affectionately called, "Oppie", that Oppenheimer believed that Wu knew everything about the absorption cross section of neutrons, a concept that would be applied when Wu joined the Manhattan Project. Wu completed her
PhD in June 1940, and was elected to
Phi Beta Kappa, the US academic honor society. In spite of Lawrence and Segrè's recommendations, she could not secure a faculty position at a university, so she remained at the Radiation Laboratory as a post-doctoral fellow. Her plans changed when the Second World War began.
World War II and the Manhattan Project (left) at the home of Mr. and Mrs.
Robert Millikan (right) on their wedding day Wu and Yuan were married at the home of
Robert Millikan, Yuan's academic supervisor and the President of Caltech, on May 30, 1942. Neither the bride's nor the groom's families were able to attend due to the outbreak of the
Pacific War. Wu and Yuan moved to the
East Coast of the United States, where Wu became an assistant professor at
Smith College, a private women's college in
Northampton, Massachusetts, while Yuan worked on
radar for
RCA. She found the job frustrating, as her duties involved teaching only, and there was no opportunity for research. She appealed to Lawrence, who wrote letters of recommendation to a number of universities. Smith responded by making Wu an associate professor and increasing her salary. She accepted a job from
Princeton University in
New Jersey as the first female faculty member in the history of the physics department, where she taught officers of the navy. In March 1944, Wu joined the
Manhattan Project's Substitute Alloy Materials (SAM) Laboratories at
Columbia University. She lived in a dormitory there, returning to Princeton on the weekends. The role of the SAM Laboratories, headed by
Harold Urey, was to support the Manhattan Project's
gaseous diffusion (
K-25) program for
uranium enrichment. Wu worked alongside
James Rainwater in a group led by
William W. Havens Jr., whose task was to develop radiation detector instrumentation. In September 1944, Wu was contacted by the Manhattan District Engineer,
Colonel Kenneth Nichols. Wu was frustrated with her lack of professorships and volunteered to help out in the project. In the beginning, Wu was assigned to check the radiation effect of the reactor by building her own instruments; later, however, she was contacted for a much bigger role. The newly commissioned
B Reactor, the first practical nuclear reactor ever built, which was located at the
Hanford Site had run into an unexpected problem, starting up and shutting down at regular intervals.
John Archibald Wheeler and partner
Enrico Fermi suspected that a
fission product,
Xe-135, with a
half-life of 9.4 hours, was the culprit, and might be a
neutron poison or absorber. Segrè then remembered the 1940 PhD thesis that Wu had done for him at Berkeley on the radioactive isotopes of Xe and told Fermi to "ask Ms. Wu". The paper on the subject was still unpublished, but after Fermi contacted Wu, Segrè visited her dorm room together with Nichols and collected the typewritten draft prepared for the
Physical Review. The suspicions of Fermi and Wheeler came true, Wu's paper unknowingly verified that Xe-135 was indeed the culprit for the B Reactor; it turned out to have an unexpectedly large
neutron absorption cross-section. Wu, wary of her publication giving information to other nations on the arms race of the war, waited for a few months before November 1944, when she and Segrè submitted a complete study on these results, which was published months before the bombs were used the next year. Wu also used her findings in radioactive uranium separation to build the standard model for producing enriched uranium to fuel the atomic bombs at the
Oak Ridge, Tennessee facility as well as build innovative
Geiger counters. Like many involved physicists in their later years, Wu later distanced herself from the Manhattan Project due to its
destructive outcome and recommended to the Taiwanese president Chiang Kai-shek in 1962 to never build nuclear weapons. However, she was pleased to know that her family was safe in China. Years later, Wu in a rare occasion opened up on her involvement in building the bomb,Do you think that people are so stupid and self-destructive? No. I have confidence in humankind. I believe we will one day live together peacefully.
Famous early experiments and academic leading career After the end of the war in August 1945, Wu accepted an offer of a position as an associate
research professor at Columbia. She would remain at Columbia for the rest of her career, and was first named
associate professor in 1952, which made her the first woman to become a tenured physics professor in university history. In November 1949, Wu experimented with the conclusions of
Einstein–Podolsky–Rosen (EPR) thought experiment, which called
quantum entanglement "spooky action at a distance". Wu was the first to establish the phenomenon and validity of entanglement using photons through observing angular correlation, as her result confirmed
Maurice Pryce and
John Clive Ward's calculations on the correlation of the quantum polarizations of two photons propagating in opposite directions. Specifically, the experiment carried out by Wu was the first important confirmation of quantum results relevant to a pair of entangled photons as applicable to the EPR paradox. In the 1970s, she carried out one of the first
Bell tests to confirm that quantum mechanics violates
Bell's inequalities. ==Chinese Civil War and permanent residency==