Who was Alan Turing's PhD advisor at Princeton University?

Alan Turing’s PhD advisor at Princeton University was Alonzo Church. Turing studied under Church from 1936 to 1938, completing his doctorate with a thesis on ordinal logics and relative computability.

Church was already a leading mathematical logician and had developed the lambda calculus, a formal system for studying functions and computation. In 1936, he had independently shown that Hilbert’s Entscheidungsproblem was unsolvable. Turing’s own work on computable numbers and Turing machines reached a closely related conclusion, and the two men’s results became foundations of the Church–Turing thesis.

Turing went to Princeton after learning about Church’s work. He received his PhD in 1938 and was offered the opportunity to remain in the United States, but returned to Britain shortly before the Second World War. Max Newman was Turing’s undergraduate mentor and later a colleague at Manchester, not his Princeton doctoral advisor. Kurt Gödel and John von Neumann were prominent Princeton figures, but neither supervised Turing’s doctorate.