Quantum weak coin flipping with a single photon

Weak coin flipping is among the fundamental cryptographic primitives which ensure the security of modern communication networks. It allows two mistrustful parties to remotely agree on a random bit when they favor opposite outcomes. Unlike other two-party computations, one can achieve information-the...

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Bibliographic Details
Published in:Physical review. A 2020-08, Vol.102 (2), Article 022414
Main Authors: Bozzio, Mathieu, Chabaud, Ulysse, Kerenidis, Iordanis, Diamanti, Eleni
Format: Article
Language:English
Subjects:
Physics
Quantum Physics
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Summary:Weak coin flipping is among the fundamental cryptographic primitives which ensure the security of modern communication networks. It allows two mistrustful parties to remotely agree on a random bit when they favor opposite outcomes. Unlike other two-party computations, one can achieve information-theoretic security using quantum mechanics only: both parties are prevented from biasing the flip with probability higher than $1/2+\epsilon$, where $\epsilon$ is arbitrarily low. Classically, the dishonest party can always cheat with probability $1$ unless computational assumptions are used. Despite its importance, no physical implementation has been proposed for quantum weak coin flipping. Here, we present a practical protocol that requires a single photon and linear optics only. We show that it is fair and balanced even when threshold single-photon detectors are used, and reaches a bias as low as $\epsilon=1/\sqrt{2}-1/2\approx 0.207$. We further show that the protocol may display quantum advantage over a few hundred meters with state-of-the-art technology.
ISSN:2469-9926
2469-9934
DOI:10.1103/PhysRevA.102.022414