{
  "annotation_id": "7ec2344c-f007-43f9-b52c-4282ff30b520",
  "date_created": "2026-03-02T18:01:48.881000Z",
  "date_modified": "2026-03-02T18:01:48.881000Z",
  "file_hash": "379ff1c628b260ea9979f26826b725e1c4b3ff0dfe40fcfbeea380e2ec419049",
  "private": false,
  "record": {
    "abstract": "We present a simple quantum network, based on the controlled-SWAP gate, that\ncan extract certain properties of quantum states without recourse to quantum\ntomography. It can be used used as a basic building block for direct quantum\nestimations of both linear and non-linear functionals of any density operator.\nThe network has many potential applications ranging from purity tests and\neigenvalue estimations to direct characterization of some properties of quantum\nchannels. Experimental realizations of the proposed network are within the\nreach of quantum technology that is currently being developed.",
    "arxiv_id": "quant-ph/0203016",
    "authors": [
      "Artur K. Ekert",
      "Carolina Moura Alves",
      "Daniel K. L. Oi",
      "Michal Horodecki",
      "Pawel Horodecki",
      "L. C. Kwek"
    ],
    "categories": [
      "quant-ph"
    ],
    "doi": "10.1103/PhysRevLett.88.217901",
    "journal_ref": "Phys. Rev. Lett. 88, 217901 (2002)",
    "title": "Direct estimations of linear and non-linear functionals of a quantum   state",
    "url": "https://arxiv.org/abs/quant-ph/0203016"
  },
  "schema_id": "dorsal/arxiv",
  "source": {
    "execution_id": "37fbd6d4-54fc-4bf5-a4e2-837b1e98b09b",
    "id": "arXiv Dataset IDs",
    "type": "Model",
    "variant": "snapshot-2026-03-01",
    "version": "0.1.0"
  },
  "user_id": 1000002
}