Optimal superdense coding through noisy channels by escorting qubits

Optimal superdense coding through noisy channels by escorting qubits | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Optimal superdense coding through noisy channels by escorting qubits Javid Ahmad Malik, Muzaffar Qadir Lone, Prince A Ganai This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8764753/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract We introduce an escort-qubit–assisted protocol that restores and stabilizes superdense coding capacity in the presence of amplitude damping channel (ADC) noise. The protocol is analyzed under three fundamental noisy configurations: amplitude damping acting on Alice’s subsystem, on Bob’s subsystem, and on both subsystems covering all practically relevant scenarios. In the absence of protection, we show that ADC effects cause a monotonic degradation of the superdense coding capacity, driving it below the classical limit in the strong decoherence regime and completely erasing the quantum advantage. Our escort-qubit protocol overcomes this limitation by coherently tracking the channel-induced Kraus trajectories during entanglement distribution. Post-selection of the no-flip trajectory, projects the shared state onto a maximally entangled resource state, thereby recovering the optimal superdense coding capacity of two classical bits, independent of the noise strength and noisy configuration. Importantly, when all ADC trajectories are taken into account, the resulting average capacity although inherently suboptimal remains strictly above both the classical limit and the unprotected capacity across the entire decoherence range. These results establish the escort-qubit protocol as a powerful, scalable, and experimentally viable approach for preserving quantum advantage and enhancing information throughput in noisy quantum communication networks. Physical sciences/Mathematics and computing Physical sciences/Physics Full Text Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-8764753","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":596172188,"identity":"4736ac1d-d22c-4876-8036-a24fbcad3ec0","order_by":0,"name":"Javid Ahmad Malik","email":"","orcid":"","institution":"National Institute of Technology Srinagar","correspondingAuthor":false,"prefix":"","firstName":"Javid","middleName":"Ahmad","lastName":"Malik","suffix":""},{"id":596172190,"identity":"9305d407-fbf2-47a4-9fa0-e8111b823587","order_by":1,"name":"Muzaffar Qadir Lone","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA+ElEQVRIiWNgGAWjYBACPjiL+eADBoYKBgYJBjCWwKmFDcFKNmBgOEOyFsY2uBbcgI299+ADxpzD9vxtzIyfK+cdlpNsYD54m4fBIg+nFp5zyQaM2w4zSxxjZpY8u+2wsTTQPmseBolinFokcswkgFrYGO73H5Bs3HY4cR4Dj5k0UEtiA24t5j+AWnjkgbb8bJwD0sL/jZAWMwagFgmDY8xsko0NhxNnM/Cw4dfCc8ZYInFbuoEhUItlw7F0Y8lmNmPLOQa4tfCz9xh++LjN2l4O6LCbDTXWchLHmx/eeFNRh1MLGCSg8JhBhAE+9aNgFIyCUTAKCAEA3lNH/QDCNuwAAAAASUVORK5CYII=","orcid":"","institution":"University of Kashmir","correspondingAuthor":true,"prefix":"","firstName":"Muzaffar","middleName":"Qadir","lastName":"Lone","suffix":""},{"id":596172191,"identity":"36866009-eda7-4959-ba89-44cef7abaa33","order_by":2,"name":"Prince A Ganai","email":"","orcid":"","institution":"National Institute of Technology Srinagar","correspondingAuthor":false,"prefix":"","firstName":"Prince","middleName":"A","lastName":"Ganai","suffix":""}],"badges":[],"createdAt":"2026-02-02 12:08:22","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-8764753/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-8764753/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":107513689,"identity":"20191521-8e48-4ca7-9f34-bb1dfcc563a1","added_by":"auto","created_at":"2026-04-22 08:12:30","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":866913,"visible":true,"origin":"","legend":"","description":"","filename":"main.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8764753/v1_covered_e2aceca9-bf66-4e0b-85ae-86ac15b527ed.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Optimal superdense coding through noisy channels by escorting qubits","fulltext":[],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":false,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":true,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":true,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-8764753/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8764753/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eWe introduce an escort-qubit–assisted protocol that restores and stabilizes superdense coding capacity in the presence of amplitude damping channel (ADC) noise. The protocol is analyzed under three fundamental noisy configurations: amplitude damping acting on Alice’s subsystem, on Bob’s subsystem, and on both subsystems covering all practically relevant scenarios. In the absence of protection, we show that ADC effects cause a monotonic degradation of the superdense coding capacity, driving it below the classical limit in the strong decoherence regime and completely erasing the quantum advantage. Our escort-qubit protocol overcomes this limitation by coherently tracking the channel-induced Kraus trajectories during entanglement distribution. Post-selection of the no-flip trajectory, \u0026nbsp;projects the shared state onto a maximally entangled resource state, thereby recovering the optimal superdense coding capacity of two classical bits, independent of the noise strength and noisy configuration. Importantly, when all ADC trajectories are taken into account, the resulting average capacity although inherently suboptimal remains strictly above both the classical limit and the unprotected capacity across the entire decoherence range. 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