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 Einstein-Podolsky-Rosen (EPR) paradox. Civil war and permanent residency After the second world war, communication with China was restored, and Wu received a letter from her family, but plans to visit China were disrupted by the civil war. Due to the civil war and communist takeover led by Mao Zedong, Wu would not return to China until decades later to meet her surviving uncle and younger brother. Though Wu did not support Mao, she also did not particularly respect the now deposed president Chiang Kai-shek and his wife Soong Mei-ling. Wu found Soong to be class-conscious, while Chiang, now president of Taiwan, was too complacent with foreign affairs and willing to let Soong handle diplomatic issues for him. However she decided to lend a bit more support to the Republic of China or Taiwan, as her teacher Hu carried close ties with the old republic. Due to the war, many were displaced and younger students would leave for the United States, while scholars in America could not return home. She missed China deeply and would often go with Luke to buy fabric to make her own qipao as a way to remember the country, which she always wore under her lab coat. Wu was also busy at this time due to the birth of her son, Vincent, in 1947.( Yuán Wěichéng). Vincent would later grow up to become a physicist like his parents and attend Columbia to follow Wu's footsteps. By the end of the civil war in 1949, Yuan joined the Brookhaven National Laboratory, and the family bought another home in Long Island. Yuan would regularly travel to Brookhaven in Long Island, and on weekends return to the family's Manhattan home near Columbia University where Wu worked as its first female physics professor. After the communists came to power in China that year, Wu's father wrote urging her not to return. Since her passport had been issued by the Kuomintang government, she found it difficult to travel abroad as places such as Switzerland did not recognize her passport. Sometimes her friend in Switzerland, physicist Wolfgang Pauli, had