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  • Open Access

Genuine Multipartite Entanglement is Not Necessary for Standard Device-Independent Conference Key Agreement

Lewis Wooltorton1,2,3,*, Peter Brown4,†, and Roger Colbeck1,‡,§

  • *Contact author: lewis.wooltorton@ens-lyon.fr
  • †Contact author: peter.brown@telecom-paris.fr
  • ‡Contact author: roger.colbeck@kcl.ac.uk
  • §Present address: Department of Mathematics, King’s College London, Strand, London, WC2R 2LS, United Kingdom.
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Phys. Rev. Lett. 135, 220803 – Published 26 November, 2025

DOI: https://doi.org/10.1103/v4s8-3zl5

Abstract

Conference key agreement aims to establish shared, private randomness among many separated parties in a network. Device-independent conference key agreement (DICKA) is a variant in which the source and the measurement devices used by each party need not be trusted. So far, DICKA protocols largely fall into two categories: those that rely on violating a joint Bell inequality using genuinely multipartite entangled states and those that concatenate many bipartite protocols. The question of whether a hybrid protocol exists, where a multipartite Bell inequality can be violated using only bipartite entanglement, was asked by Grasselli et al. [Quantum 7, 980 (2023)]. We answer this question affirmatively, by constructing an asymptotically secure DICKA protocol achieving the same rate as the concatenation of bipartite device-independent quantum key distribution, yet relying on a single joint Bell violation. Our results prompt further discussion on the benefits of multipartite entanglement for DICKA over its bipartite alternative, and we give an overview of different arguments for near-term devices.

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Outline

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Phys. Rev. Lett. 135, 220803– Published 26 November, 2025
  • Received 1 April 2025
  • Accepted 25 September 2025
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.

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