{
  "annotation_id": "c5cc0510-c50b-4bba-a597-4190bc552f09",
  "date_created": "2026-03-02T18:02:09.996000Z",
  "date_modified": "2026-03-02T18:02:09.996000Z",
  "file_hash": "4471fb0e0ddc04398a29860bb5389fc2174ae5581f98f852068920f2c098ea3a",
  "private": false,
  "record": {
    "abstract": "We present an easy way of observing superluminal group velocities using a\nbirefringent optical fiber and other standard devices. In the theoretical\nanalysis, we show that the optical properties of the setup can be described\nusing the notion of \"weak value\". The experiment shows that the group velocity\ncan indeed exceed c in the fiber; and we report the first direct observation of\nthe so-called \"signal velocity\", the speed at which information propagates and\nthat cannot exceed c.",
    "arxiv_id": "quant-ph/0407155",
    "authors": [
      "Nicolas Brunner",
      "Valerio Scarani",
      "Mark Wegmuller",
      "Matthieu Legre",
      "Nicolas Gisin"
    ],
    "categories": [
      "quant-ph"
    ],
    "doi": "10.1103/PhysRevLett.93.203902",
    "journal_ref": "Phys. Rev. Lett. 93, 203902 (2004)",
    "title": "Direct measurement of superluminal group velocity and of signal velocity   in an optical fiber",
    "url": "https://arxiv.org/abs/quant-ph/0407155"
  },
  "schema_id": "dorsal/arxiv",
  "source": {
    "execution_id": "0ad7d55a-b1e2-4684-b077-bd0a31b38e6b",
    "id": "arXiv Dataset IDs",
    "type": "Model",
    "variant": "snapshot-2026-03-01",
    "version": "0.1.0"
  },
  "user_id": 1000002
}