Computer scientist and TPS alumnus Daniel Spielman '84, working with his postdoc Adam Marcus and his graduate student Nikhil Srivastava, succeeded in solving the famous Kadison-Singer problem, a question about the foundations of quantum physics that had remained unsolved for almost 50 years.
According to a recent article in Quanta Magazine, "Word spread quickly through the mathematics community that one of the paramount problems in C*-algebras and a host of other fields had been solved by three outsiders — computer scientists who had barely a nodding acquaintance with the disciplines at the heart of the problem."
Daniel (or Danny, as he was known around TPS) is the Henry Ford II professor of Computer Science, Mathematics, and Applied Mathematics at Yale University; a Simons Investigator; and a MacArthur Fellow. He is the Director of Undergraduate Studies for Applied Mathematics and the co-Director of the Yale Institute for Network Science (YINS).
Here is a link to the Quanta article. In the photograph below, Danny is on the right (photo credit A. Marcus).