Absorption-Based Qubit Estimation in Discrete-Time Quantum Walks

Quantum Physics arXiv:2512.02186 (quant-ph) [Submitted on 1 Dec 2025] Title:Absorption-Based Qubit Estimation in Discrete-Time Quantum Walks Authors:Edgard P. M. Amorim, Lorena R. Cerutti, O. P. de Sá Neto, M. C. de Oliveira View a PDF of the paper titled Absorption-Based Qubit Estimation in Discrete-Time Quantum Walks, by Edgard P. M. Amorim and 3 other authors View PDF HTML (experimental) Abstract:We investigate state estimation in discrete-time quantum walks with a single absorbing boundary. Using a spectral approach, we obtain closed expressions for the escape probability as a function of the coin state and the boundary position, and their corresponding classical Fisher information for a simple absorption readout. Comparing with the single-copy quantum Fisher information shows a clear complementarity: near boundaries carry broad information about the population angle of the coin, whereas moderate or distant boundaries reveal phase-sensitive regions. Because a single boundary probes only one information direction, combining two boundary placements yields a full-rank Fisher matrix and tight joint Cramér--Rao bounds, while retaining a binary, tomography-free measurement. We outline an integrated-photonics implementation in which an on-chip sink realizes the absorber and estimate a substantial reduction in configuration count compared to mode-resolved qubit tomography. These results identify absorption in quantum walks as a simple and scalable primitive for coin-state metrology. Comments: Subjects: Quantum Physics (quant-ph) Cite as: arXiv:2512.02186 [quant-ph] (or arXiv:2512.02186v1 [quant-ph] for this version) https://doi.org/10.48550/arXiv.2512.02186 Focus to learn more arXiv-issued DOI via DataCite Submission history From: Edgard Amorim [view email] [v1] Mon, 1 Dec 2025 20:28:44 UTC (2,992 KB) Full-text links: Access Paper: View a PDF of the paper titled Absorption-Based Qubit Estimation in Discrete-Time Quantum Walks, by Edgard P. M. Amorim and 3 other authorsView PDFHTML (experimental)TeX Source view license Current browse context: quant-ph new | recent | 2025-12 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?)