{
  "abstract": "A system between a preparation and a post-selection has had no agreed state since 1964. With positivity as the criterion, a post-selection admits an interval of orderings around the symmetric one exactly when the subspace it forbids is spanned by eigenvectors of a full-rank filtered state. Otherwise it certifies contextuality, testable on a qubit. The averaged filtered state carries the entanglement spectrum of the record, so the smallest forbidden subspaces a symmetry allows are even-dimensional in the Haldane class and odd in the trivial one. That parity is the record's topological class.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2609.17307",
  "author_total": 2,
  "authors": [
    {
      "name": "Chon-Fai Kam"
    },
    {
      "name": "Kai-Wen Wong"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/8x2f34pfdhdaa.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2609.17307",
  "fulltext_url": null,
  "id": "8x2f34pfdhdaa",
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  "landing_url": "https://arxiv.org/abs/2609.17307",
  "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",
      "3107|Quantum Mechanics and Applications"
    ]
  ],
  "openalex": "W7213422785",
  "pdf_url": "https://arxiv.org/pdf/2609.17307",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-15",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/8x2f34pfdhdaa.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:21:41Z",
      "native_id": "2609.17307",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2609.17307"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "arxiv:quant-ph",
      "subfield": "quantum"
    }
  ],
  "title": "Forbidden Subspaces in Quantum State Smoothing",
  "title_text": "Forbidden Subspaces in Quantum State Smoothing",
  "type": "preprint",
  "updated_at": "2026-10-30T12:21:41Z",
  "url": "https://research.draconitic.com/paper/8x2f34pfdhdaa",
  "venue": "arXiv",
  "versions": []
}