Quantum weak coin-flipping with bias of 0.192

摘要

We present a family of protocols for flipping a coin over a telephone in a quantum mechanical setting. The family contains protocols with n + 2 messages for all n < 1, and asymptotically achieves a bias of 0.192. The case n = 2 is equivalent to the protocol of Spekkens and Rudolph with bias 0.207, which was the best known protocol. The case n = 3 achieves a bias of 0.199, and n = 8 achieves a bias of 0.193. The analysis of the protocols uses Kitaev's description of coin-flipping as a semidefinite program. We construct an analytical solution to the dual problem which provides an upper bound on the amount that a party can cheat.