Title | The impossibility of efficient quantum weak coin flipping |

Publication Type | Journal Article |

Year of Publication | 2020 |

Authors | Miller, C |

Journal | STOC 2020: Proceedings of the 52nd Annual ACM SIGACT Symposium on Theory of Computing |

Pages | 916-929 |

Date Published | 6/2020 |

Abstract | How can two parties with competing interests carry out a fair coin flip across a quantum communication channel? This problem (quantum weak coin-flipping) was formalized more than 15 years ago, and, despite some phenomenal theoretical progress, practical quantum coin-flipping protocols with vanishing bias have proved hard to find. In the current work we show that there is a reason that practical weak quantum coin-flipping is difficult: any quantum weak coin-flipping protocol with bias є must use at least exp( Ω (1/√є )) rounds of communication. This is a large improvement over the previous best known lower bound of Ω ( log log(1/є )) due to Ambainis from 2004. Our proof is based on a theoretical construction (the two-variable profile function) which may find further applications. |

DOI | 10.1145/3357713.3384276 |