{
  "abstract": "In quantum metrology, adaptive and causal-superposition strategies are proven to be beneficial over parallel schemes for a finite number of channel uses, but their advantages disappear in the asymptotic limit. We show that quantum operations with indefinite time direction, specifically, time-flip (TF)-assisted strategies, referred to as indefinite time-directed metrology (ITDM), can overcome this asymptotic equivalence. Using semidefinite programming, we rigorously demonstrate that TF-assisted protocols can achieve quantum Fisher information (QFI) strictly exceeding the maximum value attainable by parallel, adaptive, and causal-superposition strategies, both for finite and asymptotically many channel uses. Moreover, we identify a class of Pauli noise channels for which ITDM achieves Heisenberg scaling, while all parallel, adaptive, and causal-superposition strategies remain restricted to standard scaling. We call this phenomenon as metrological activation. Interestingly, this activation can be used to exhibit that the quantum time-flip and transposition supermaps cannot be simulated by conventional quantum circuits or causal-superposition strategies using any finite number of channel queries, thereby establishing indefinite time direction as a genuine resource for quantum metrology.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2609.01175",
  "author_total": 3,
  "authors": [
    {
      "name": "Gaurang Agrawal"
    },
    {
      "name": "Pritam Halder"
    },
    {
      "name": "Aditi Sen De"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/ennwhbj9a2sfa.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2609.01175",
  "fulltext_url": null,
  "id": "ennwhbj9a2sfa",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2609.01175",
  "language": null,
  "licence": "LicenseRef-arXiv-nonexclusive-1.0",
  "licence_label": "arXiv licence",
  "licence_source": "article",
  "licence_url": "http://arxiv.org/licenses/nonexclusive-distrib/1.0/",
  "metadata_licence": "CC0-1.0",
  "native_subjects": [
    [
      "arxiv",
      "quant-ph"
    ],
    [
      "openalex",
      "1702|Quantum Information and Cryptography"
    ]
  ],
  "openalex": "W7206159888",
  "pdf_url": "https://arxiv.org/pdf/2609.01175",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-01",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/ennwhbj9a2sfa.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:18:00Z",
      "native_id": "2609.01175",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2609.01175"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "arxiv:quant-ph",
      "subfield": "quantum"
    }
  ],
  "title": "Quantum time-flip beats adaptive metrology: Asymptotic benefit, activation, and unsimulability",
  "title_text": "Quantum time-flip beats adaptive metrology: Asymptotic benefit, activation, and unsimulability",
  "type": "preprint",
  "updated_at": "2026-10-30T12:18:00Z",
  "url": "https://research.draconitic.com/paper/ennwhbj9a2sfa",
  "venue": "arXiv",
  "versions": []
}