{
  "annotation_id": "1271f6e5-1bac-4fed-87d6-2e53802c531a",
  "date_created": "2026-03-02T18:02:37.923000Z",
  "date_modified": "2026-03-02T18:02:37.923000Z",
  "file_hash": "61b607dbd4393ab3b2c8c48cea6d3c7bd85355b4309426b6f1e6e1b821bfea2e",
  "private": false,
  "record": {
    "abstract": "We explore the sense in which the state of a physical system may or may not\nbe regarded (an) observable in quantum mechanics. Simple and general arguments\nfrom various lines of approach are reviewed which demonstrate the following\nno-go claims: (1) the structure of quantum mechanics precludes the\ndetermination of the state of a single system by means of measurements\nperformed on that system only; (2) there is no way of using entangled\ntwo-particle states to transmit superluminal signals. Employing the\nrepresentation of observables as general positive operator valued measures, our\nanalysis allows one to indicate whether optimal separation of different states\nis achieved by means of sharp or unsharp observables.",
    "arxiv_id": "quant-ph/9604014",
    "authors": [
      "P. Busch"
    ],
    "categories": [
      "quant-ph"
    ],
    "journal_ref": "In: \"Potentiality, Entanglement and Passion-at-a-Distance: Quantum\n  Mechanical Studies for Abner Shimony.\" Eds. R.S. Cohen, M.A. Horne, J.\n  Stachel, Kluwer, Dordrecht, 1997, pp. 61-70.",
    "title": "Is the quantum state (an) observable?",
    "url": "https://arxiv.org/abs/quant-ph/9604014"
  },
  "schema_id": "dorsal/arxiv",
  "source": {
    "execution_id": "caf630e3-7464-47d5-82bd-37632cd2f29f",
    "id": "arXiv Dataset IDs",
    "type": "Model",
    "variant": "snapshot-2026-03-01",
    "version": "0.1.0"
  },
  "user_id": 1000002
}