Richard Feynman, the pioneer of quantum computing, wrote in his 1982 book Simulating Physics with Computers: “The only difference between a probabilistic classical world and the equations of the quantum world is that somehow or other it appears as if the probabilities would have to go negative.”

Negative probabilities make no sense. Yet they are tolerated in quantum tomography and elsewhere. So what reality, or at least intuition, is behind negative probabilities? A related question is what negative probabilities are good for.

We address these and related questions. The talk does not presume quantum expertise, though having such expertise would be helpful of course.

Bio: Yuri Gurevich is Professor Emeritus at the University of Michigan. The last 20 years of his career he spent at Microsoft Research as a Principal Researcher. He is a Fellow of AAAS, ACM, EATCS, and Guggenheim, a foreign member of Academia Europaea, and Dr. Honoris Causa of a Belgian and a Russian university.