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Preprocessing noise in finite-size quantum key distribution

arXiv Quantum Physics
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⚡ Quantum Brief
Researchers analyzed how preprocessing noise enhances quantum key distribution (QKD) in finite-size systems, where signal exchanges are limited. Their study builds on prior work showing trusted noise can extend error tolerance beyond the 11% QBER threshold in asymptotic BB84 protocols. Using sandwiched Rényi entropy and a two-step Frank-Wolfe optimization, they derived tight numerical bounds for key rates under trusted flipping probability. Noise benefits were confined to a narrow α-range (1 to ~1.4), revealing finite-size constraints. Optimizing α improved finite-size key rates across QBER values, demonstrating noise-enhanced performance in both asymptotic and practical regimes. This challenges assumptions about noise’s role in real-world QKD deployments. The team quantified maximum tolerable QBER as a function of block size, offering a roadmap for designing noise-resilient finite-size QKD systems with higher error thresholds. Results suggest preprocessing noise could be a low-cost tool to boost key rates in near-term quantum networks, where finite resources limit performance. The findings bridge theory and experimental QKD implementations.
Preprocessing noise in finite-size quantum key distribution

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Quantum Physics arXiv:2603.18213 (quant-ph) [Submitted on 18 Mar 2026] Title:Preprocessing noise in finite-size quantum key distribution Authors:Gabriele Staffieri, Giuseppe D'Ambruoso, Giovanni Scala, Cosmo Lupo View a PDF of the paper titled Preprocessing noise in finite-size quantum key distribution, by Gabriele Staffieri and 3 other authors View PDF HTML (experimental) Abstract:It is known that preprocessing noise may boost quantum key distribution by expanding the range of values of tolerated noise. For BB84, adding trusted noise may allow the generation of secret keys even for qubit error rate (QBER) beyond the 11% threshold in the asymptotic regime. Here we study the effect of preprocessing noise in the finite-size regime where only a limited number of signals are exchanged between Alice and Bob. We compute tight numerical lower bounds in terms of the sandwiched Rényi entropy of order alpha, optimized via a two-step Frank-Wolfe algorithm, in the presence of a trusted flipping probability q. We find that trusted noise improves the key rate only for a finite interval of alpha, from the alpha -> 1 limit up to alpha approx 1.4. By optimizing on the value of alpha, we determine finite-size key rates for different values of the QBER, observing enhancement due to trusted noise both in asymptotic and finite-size regimes. Finally, we determine the maximum tolerable QBER as a function of the block size. Comments: Subjects: Quantum Physics (quant-ph) Cite as: arXiv:2603.18213 [quant-ph] (or arXiv:2603.18213v1 [quant-ph] for this version) https://doi.org/10.48550/arXiv.2603.18213 Focus to learn more arXiv-issued DOI via DataCite (pending registration) Submission history From: Gabriele Staffieri [view email] [v1] Wed, 18 Mar 2026 19:00:01 UTC (1,738 KB) Full-text links: Access Paper: View a PDF of the paper titled Preprocessing noise in finite-size quantum key distribution, by Gabriele Staffieri and 3 other authorsView PDFHTML (experimental)TeX Source view license Current browse context: quant-ph new | recent | 2026-03 References & Citations INSPIRE HEP NASA ADSGoogle Scholar Semantic Scholar export BibTeX citation Loading... BibTeX formatted citation × loading... Data provided by: Bookmark Bibliographic Tools Bibliographic and Citation Tools Bibliographic Explorer Toggle Bibliographic Explorer (What is the Explorer?) Connected Papers Toggle Connected Papers (What is Connected Papers?) Litmaps Toggle Litmaps (What is Litmaps?) scite.ai Toggle scite Smart Citations (What are Smart Citations?) Code, Data, Media Code, Data and Media Associated with this Article alphaXiv Toggle alphaXiv (What is alphaXiv?) Links to Code Toggle CatalyzeX Code Finder for Papers (What is CatalyzeX?) DagsHub Toggle DagsHub (What is DagsHub?) GotitPub Toggle Gotit.pub (What is GotitPub?) Huggingface Toggle Hugging Face (What is Huggingface?) Links to Code Toggle Papers with Code (What is Papers with Code?) ScienceCast Toggle ScienceCast (What is ScienceCast?) Demos Demos Replicate Toggle Replicate (What is Replicate?) Spaces Toggle Hugging Face Spaces (What is Spaces?) Spaces Toggle TXYZ.AI (What is TXYZ.AI?) Related Papers Recommenders and Search Tools Link to Influence Flower Influence Flower (What are Influence Flowers?) Core recommender toggle CORE Recommender (What is CORE?) Author Venue Institution Topic About arXivLabs arXivLabs: experimental projects with community collaborators arXivLabs is a framework that allows collaborators to develop and share new arXiv features directly on our website. Both individuals and organizations that work with arXivLabs have embraced and accepted our values of openness, community, excellence, and user data privacy. arXiv is committed to these values and only works with partners that adhere to them. Have an idea for a project that will add value for arXiv's community? Learn more about arXivLabs. Which authors of this paper are endorsers? | Disable MathJax (What is MathJax?)

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Source: arXiv Quantum Physics