High-rate multipartite quantum secret sharing with composable security

Abstract:Future quantum communication networks will conceivably support cryptographic tasks that require entanglement among more than two users. Quantum secret sharing is a prime example where entanglement provides a direct means to coordinate untrusted parties with security from eavesdropping in a multi-party setting. However, the canonical GHZ-based protocols can be vulnerable to participant attacks, in which untrusted parties try to learn the secret without collaborating. Here, we experimentally evaluate a discrete-variable $(n,n)$-threshold quantum secret-sharing protocol whose finite-key analysis provides composable security against general attacks, including participant attacks. Using two domain-engineered entangled photon pair sources, we generate 4-qubit GHZ states at rates above $5\times10^3$ fourfold events per second and a maximum asymptotic secret key rate of $750 \pm 10$ bits per second. We then distribute the state through a 4-arm star network comprising 20km of fibre in total. From the measured event rates and error statistics, we infer that a randomised 24-hour execution with the optimised basis probability would yield a composable finite-key lower bound of 8.7 Mbits, under the assumption that the measured source and device statistics remain stationary.

arXiv:2609.13367 [quant-ph]

(or arXiv:2609.13367v1 [quant-ph] for this version)

https://doi.org/10.48550/arXiv.2609.13367 Focus to learn more arXiv-issued DOI via DataCite (pending registration)

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