Multiparty Quantum Coin Flipping
<|reference_start|>Multiparty Quantum Coin Flipping: We investigate coin-flipping protocols for multiple parties in a quantum broadcast setting:   (1) We propose and motivate a definition for quantum broadcast. Our model of quantum broadcast channel is new.   (2) We discovered that quantum broadcast is essentially a combination of pairwise quantum channels and a classical broadcast channel. This is a somewhat surprising conclusion, but helps us in both our lower and upper bounds.   (3) We provide tight upper and lower bounds on the optimal bias epsilon of a coin which can be flipped by k parties of which exactly g parties are honest: for any 1 <= g <= k, epsilon = 1/2 - Theta(g/k).   Thus, as long as a constant fraction of the players are honest, they can prevent the coin from being fixed with at least a constant probability. This result stands in sharp contrast with the classical setting, where no non-trivial coin-flipping is possible when g <= k/2.<|reference_end|>
@article{ambainis2003multiparty,
    title={Multiparty Quantum Coin Flipping},
    author={Andris Ambainis, Harry Buhrman, Yevgeniy Dodis and Hein Roehrig},
    journal={arXiv preprint arXiv:quant-ph/0304112},
    year={2003},
    doi={10.1109/CCC.2004.1313848},
    archivePrefix={arXiv},
    eprint={quant-ph/0304112},
    primaryClass={quant-ph cs.CR cs.DC}
}