{
  "annotation_id": "c31442f2-76f3-430c-9207-5c263f1ac61b",
  "date_created": "2026-03-02T18:02:07.105000Z",
  "date_modified": "2026-03-02T18:02:07.105000Z",
  "file_hash": "1071f6367ccd1fccb523bcdd520eb1526c3534dffc3e38228551f5885a9d92a0",
  "private": false,
  "record": {
    "abstract": "We study macroscopic observables defined as the total value of a physical\nquantity over a collection of quantum systems. We show that previous results\nobtained for infinite ensemble of identically prepared systems lead to\nincorrect conclusions for finite ensembles. In particular, exact measurement of\na macroscopic observable significantly disturbs the state of any finite\nensemble. However, we show how this disturbance can be made arbitrarily small\nwhen the measurement are of finite accuracy. We demonstrate a tradeoff between\nstate disturbance and measurement coarseness as a function of the size of the\nensemble. Using this tradeoff, we show that the histories generated by any\nsequence of finite accuracy macroscopic measurements always generate a\nconsistent family in the absence of large scale entanglement, for sufficiently\nlarge ensembles. Hence, macroscopic observables behave \"classically\" provided\nthat their accuracy is coarser than the quantum correlation length-scale of the\nsystem. The role of these observable is also discussed in the context of NMR\nquantum information processing and bulk ensemble quantum state tomography.",
    "arxiv_id": "quant-ph/0403212",
    "authors": [
      "David Poulin"
    ],
    "categories": [
      "quant-ph"
    ],
    "doi": "10.1103/PhysRevA.71.022102",
    "journal_ref": "Phys. Rev. A 71, 22102 (2005)",
    "title": "Macroscopic Observables",
    "url": "https://arxiv.org/abs/quant-ph/0403212"
  },
  "schema_id": "dorsal/arxiv",
  "source": {
    "execution_id": "0efdb50b-9617-4512-97e3-c0a5319f26d8",
    "id": "arXiv Dataset IDs",
    "type": "Model",
    "variant": "snapshot-2026-03-01",
    "version": "0.1.0"
  },
  "user_id": 1000002
}