{
  "abstract": "In the quantum state distinguishing problem, an algorithm is given copies of a state $|ψ\\rangle$ or $|ϕ\\rangle$ separated by trace distance $\\varepsilon$, and tasked with deciding which is the case. It is a standard result that $Θ(\\varepsilon^{-2})$ copies are required, while having access to a unitary state preparation oracle and its inverse improves this to $Θ(\\varepsilon^{-1})$ queries. We study the intermediate case with forward-only access, capturing scenarios where the oracle is a physical process that cannot be reversed. Tang and Wright recently showed that distinguishing a known state from an \\emph{unknown} close state requires $Ω(\\varepsilon^{-2})$ forward queries in high dimension; we strengthen this result by proving the same bound even when both states are known, as in the state distinguishing setting. Moreover, our lower bound uses a direct hybrid argument, avoiding advanced compressed oracle techniques used in the prior work. In contrast, we give a dimension-independent algorithm solving a continuous-time variant of state distinguishing with only $O(\\varepsilon^{-1})$ total forward evolution time. The algorithm uses quantum Zeno dynamics to confine evolution to a known two-dimensional subspace. Thus, a quadratic advantage survives without inverse access for a natural continuous-time analogue of state distinguishing.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2610.05389",
  "author_total": 3,
  "authors": [
    {
      "name": "Emma Wang"
    },
    {
      "name": "Joseph Carolan"
    },
    {
      "name": "Andrew M. Childs"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/61k1tyfc4hrsv.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2610.05389",
  "fulltext_url": null,
  "id": "61k1tyfc4hrsv",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2610.05389",
  "language": null,
  "licence": "CC-BY-4.0",
  "licence_label": "CC BY 4.0",
  "licence_source": "article",
  "licence_url": "http://creativecommons.org/licenses/by/4.0/",
  "metadata_licence": "CC0-1.0",
  "native_subjects": [
    [
      "arxiv",
      "quant-ph"
    ],
    [
      "openalex",
      "1702|Quantum Computing Algorithms and Architecture"
    ]
  ],
  "openalex": "W7220659121",
  "pdf_url": "https://arxiv.org/pdf/2610.05389",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-04",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/61k1tyfc4hrsv.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:27:01Z",
      "native_id": "2610.05389",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2610.05389"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "arxiv:quant-ph",
      "subfield": "quantum"
    }
  ],
  "title": "On State Distinguishing Without Inverse Queries",
  "title_text": "On State Distinguishing Without Inverse Queries",
  "type": "preprint",
  "updated_at": "2026-10-30T12:27:01Z",
  "url": "https://research.draconitic.com/paper/61k1tyfc4hrsv",
  "venue": "arXiv",
  "versions": []
}