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Memory effects in repeated uses of quantum channels

Hayden Zammit, Roberto Salazar, Gianluca Valentino, Johann A. Briffa, Tony J. G. Apollaro
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⚡ Quantum Brief
Researchers from Malta and Italy reveal that repeatedly using quantum channels without resetting them introduces memory effects that degrade performance, challenging conventional memoryless channel assumptions in quantum networks. The team derived an analytical formula calculating the average fidelity of quantum state transfer (QST) after multiple uses of U(1)-symmetric channels, providing a tool to quantify cumulative errors in continuous operations. A case study of a perfect QST channel with minor readout timing errors showed even small imperfections create significant memory effects, drastically reducing fidelity in subsequent transmissions. The findings highlight the resource and time costs of resetting channels, proposing that understanding memory effects could optimize quantum networks for distributed computing and key distribution. This work shifts focus from idealized memoryless models to practical, continuous-use scenarios, addressing a critical gap in quantum communication protocols.
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Quantum Physics arXiv:2511.05661 (quant-ph) [Submitted on 7 Nov 2025] Title:Memory effects in repeated uses of quantum channels Authors:Hayden Zammit, Roberto Salazar, Gianluca Valentino, Johann A. Briffa, Tony J. G. Apollaro View a PDF of the paper titled Memory effects in repeated uses of quantum channels, by Hayden Zammit and 4 other authors View PDF HTML (experimental) Abstract:Quantum Information Processing (QIP) tasks can be efficiently formulated in terms of quantum dynamical maps, whose formalism is able to provide the appropriate mathematical representation of the evolution of open quantum systems. A key QIP task is quantum state transfer (QST) aimed at sharing quantum information between distant nodes of a quantum network, enabling, e.g. quantum key distribution and distributed quantum computing. QST has primarily been addressed insofar by resetting the quantum channel after each use, thus giving rise to memoryless channels. Here we consider the case where the quantum channel is continuously used, without implementing time- and resource- consuming resetting operations. We derive a general, analytical expression for the $n^{\mathrm{th}}$-use average QST fidelity for $U(1)$-symmetric channels and apply our formalism to a perfect QST channel in the presence of imperfect readout timing. We show that even relatively small readout timing errors give rise to memory effects which have a highly detrimental impact on subsequent QST tasks. Comments: Subjects: Quantum Physics (quant-ph) Cite as: arXiv:2511.05661 [quant-ph] (or arXiv:2511.05661v1 [quant-ph] for this version) https://doi.org/10.48550/arXiv.2511.05661 Focus to learn more arXiv-issued DOI via DataCite (pending registration) Submission history From: Hayden Zammit [view email] [v1] Fri, 7 Nov 2025 19:00:14 UTC (714 KB) Full-text links: Access Paper: View a PDF of the paper titled Memory effects in repeated uses of quantum channels, by Hayden Zammit and 4 other authorsView PDFHTML (experimental)TeX Source view license Current browse context: quant-ph new | recent | 2025-11 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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