Abstract: How can two parties who are at a distance from one another carry out a fair coin flip? This problem has been an object of study for decades. Previous research has shown that coin flipping with positive bias (i.e., coin-flipping which permits a limited amount of cheating) is possible if the parties share a quantum information channel. Yet, proving quantum coin-flipping with bias tending to zero is mysteriously hard -- the only known protocol requires more than an exponential amount of communication.
This talk will be about a new result which untangles the mystery of why quantum coin-flipping is difficult. We will draw on some unexpected topics in mathematics (including the behavior of rational functions on complex numbers). Since this talk is aimed for a broad audience, the first half will be spent covering fundamental concepts and giving a detailed description of the central problem. The talk is based on https://arxiv.org/abs/1909.10103 .
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