Quantum flip

Rainie York

Satoshi Ishizaka, Alexander I. Lvovsky

A biased quantum coin flip (QCF) does not realize the functionality of a classical black‐boxed coin flip, if it satisfies some fidelity condition. We consider a quantum black‐boxed coin flip and show that the fidelity condition is well‐explained as the functionality of the quantum black‐boxed coin flip. Moreover, we show the results of the security analysis for a QCF like protocol.

Mike Post

Satoshi Ishizaka

We show that a biased quantum coin flip (QCF) cannot provide the performance of a black-boxed biased coin flip, if it satisfies some fidelity conditions. Although such a QCF satisfies the security conditions of a biased coin flip, it does not realize the ideal functionality and, therefore, does not satisfy the demands for universally composable security. Moreover, through a comparison within a small restricted bias range, we show that an arbitrary QCF is distinguishable from a black-boxed coin flip unless it is unbiased on both sides of parties against insensitive cheating. We also point out the difficulty in developing cheat-sensitive quantum bit commitment in terms of the uncomposability of a QCF.

Carlos Mochon

"God does not play dice. He flips coins instead." And though for some reason He has denied us quantum bit commitment. And though for some reason he has even denied us strong coin flipping. He has, in His infinite mercy, granted us quantum weak coin flipping so that we too may flip coins. Instructions for the flipping of coins are contained herein. But be warned! Only those who have mastered Kitaev's formalism relating coin flipping and operator monotone functions may succeed. For those foolhardy enough to even try, a complete tutorial is included.

Mariette DiChristina