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The uncloneable bit exists

arXiv Quantum Physics
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⚡ Quantum Brief
Researchers Archishna Bhattacharyya, Anne Broadbent, and Eric Culf proved the existence of an uncloneable quantum bit, achieving unconditional security in encryption where two non-communicating adversaries cannot simultaneously decrypt a single ciphertext—even with the key. Their construction leverages quantum information principles, including monogamy of entanglement via strong subadditivity, to prevent high correlation between the sender and multiple adversaries, ensuring no coordinated attack outperforms random guessing. The protocol’s security approaches ideal limits exponentially with the security parameter, requiring no computational assumptions, unlike classical cryptography, which relies on unproven hardness assumptions. A novel decoupling step certifies statistical independence for randomness extraction, formalizing a physically enforced cryptographic primitive impossible in classical systems, marking a fundamental breakthrough in quantum cryptography. This work establishes uncloneability as a natural quantum property, delineating a new class of information-theoretic security guarantees rooted in the laws of quantum mechanics.
The uncloneable bit exists

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Quantum Physics arXiv:2603.08916 (quant-ph) [Submitted on 9 Mar 2026] Title:The uncloneable bit exists Authors:Archishna Bhattacharyya, Anne Broadbent, Eric Culf View a PDF of the paper titled The uncloneable bit exists, by Archishna Bhattacharyya and 1 other authors View PDF HTML (experimental) Abstract:We establish quantum uncloneable encryption with unconditional security, preventing two non-communicating adversaries from simultaneously decrypting a single ciphertext $-$ even when both are given the key. Our construction achieves security that approaches the ideal limit at a rate that is exponentially small in the security parameter, without employing any assumptions. Our proof invokes quantum information principles in the fully quantum realm, in a novel setting of cryptography. A decoupling step certifies the statistical independence needed for randomness extraction, and monogamy of entanglement, formalised via strong subadditivity, rules out the sender being highly correlated with two non-communicating adversaries at once. Consequently, no coordinated strategy beats random guessing of the encrypted bit, establishing unconditional uncloneability. This reveals the existence of an uncloneable bit in Nature and delineates a fundamental, physically enforced cryptographic primitive unavailable in classical settings. Comments: Subjects: Quantum Physics (quant-ph) Cite as: arXiv:2603.08916 [quant-ph] (or arXiv:2603.08916v1 [quant-ph] for this version) https://doi.org/10.48550/arXiv.2603.08916 Focus to learn more arXiv-issued DOI via DataCite (pending registration) Submission history From: Archishna Bhattacharyya [view email] [v1] Mon, 9 Mar 2026 20:33:33 UTC (847 KB) Full-text links: Access Paper: View a PDF of the paper titled The uncloneable bit exists, by Archishna Bhattacharyya and 1 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