Experimental quantum tossing of a single coin

TL;DR

This paper demonstrates an all-optical fiber experiment for quantum coin tossing, showing it can produce randomness surpassing classical limits despite experimental imperfections, and discusses potential cheating strategies.

Contribution

It provides the first experimental realization of quantum coin tossing with higher randomness than classical protocols, accounting for real-world imperfections.

Findings

Quantum coin tossing exceeds classical randomness limits.

Experimental imperfections are crucial in performance comparison.

Cheating strategies can be implemented by both parties.

Abstract

The cryptographic protocol of coin tossing consists of two parties, Alice and Bob, that do not trust each other, but want to generate a random bit. If the parties use a classical communication channel and have unlimited computational resources, one of them can always cheat perfectly. Here we analyze in detail how the performance of a quantum coin tossing experiment should be compared to classical protocols, taking into account the inevitable experimental imperfections. We then report an all-optical fiber experiment in which a single coin is tossed whose randomness is higher than achievable by any classical protocol and present some easily realisable cheating strategies by Alice and Bob.