https://hal.archives-ouvertes.fr/hal-02495409Bozzio, MathieuMathieuBozzioIQA - Information Quantique et Applications - LTCI - Laboratoire Traitement et Communication de l'Information - IMT - Institut Mines-Télécom [Paris] - Télécom ParisQI - Information Quantique [LIP6] - LIP6 - SU - Sorbonne Université - CNRS - Centre National de la Recherche ScientifiqueChabaud, UlysseUlysseChabaudQI - Information Quantique [LIP6] - LIP6 - SU - Sorbonne Université - CNRS - Centre National de la Recherche ScientifiqueKerenidis, IordanisIordanisKerenidisIRIF (UMR_8243) - Institut de Recherche en Informatique Fondamentale - UPD7 - Université Paris Diderot - Paris 7 - CNRS - Centre National de la Recherche ScientifiqueDiamanti, EleniEleniDiamantiQI - Information Quantique [LIP6] - LIP6 - SU - Sorbonne Université - CNRS - Centre National de la Recherche ScientifiqueQuantum weak coin flipping with a single photonHAL CCSD2020[PHYS.QPHY] Physics [physics]/Quantum Physics [quant-ph]Chabaud, Ulysse2020-03-02 08:22:242022-09-06 13:27:192020-03-02 08:22:24enJournal articles10.1103/PhysRevA.102.0224141Weak 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.