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Long-range photonic device-independent quantum key distribution using spontaneous parametric down-conversion sources and linear optics

Morteza Moradi1, Maryam Afsary1, Piotr Mironowicz2,3, Enky Oudot4,5, and Magdalena Stobińska-Moretto6,*

  • *Contact author: magdalena.stobinska@gmail.com
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Phys. Rev. Research 8, 023290 – Published 12 June, 2026

DOI: https://doi.org/10.1103/ycd9-nc6q

Abstract

We address the question of the implementation of long-distance device-independent quantum key distribution (DI QKD) by proposing two experimentally viable schemes. Those schemes use only spontaneous parametric down-conversion sources and linear optics. They achieve favorable key rate scaling proportional to the square root of channel transmittance ηt, matching the twin-field protocol advantage. We demonstrate positive asymptotic key rates at detector efficiencies as low as 80%, bringing DI QKD within the reach of current superconducting detector technology. Our security analysis employs the entropy accumulation theorem to establish rigorous finite-size bounds, achieving finite-key rates at a detector efficiency of 90%. This work represents a critical milestone toward device-independent security in quantum communication networks, providing experimentalists with practical implementation pathways while maintaining the strongest possible security guarantees against quantum adversaries.

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Phys. Rev. Research 8, 023290– Published 12 June, 2026
  • Received 30 August 2025
  • Accepted 6 May 2026
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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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