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Quantum weak coin flipping with a single photon

Abstract : 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.
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Contributor : Ulysse Chabaud <>
Submitted on : Monday, March 2, 2020 - 8:22:24 AM
Last modification on : Tuesday, March 23, 2021 - 9:28:03 AM

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Mathieu Bozzio, Ulysse Chabaud, Iordanis Kerenidis, Eleni Diamanti. Quantum weak coin flipping with a single photon. Physical Review A, American Physical Society 2020, 102 (2), pp.022414. ⟨10.1103/PhysRevA.102.022414⟩. ⟨hal-02495409⟩



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