{
  "annotation_id": "b0b315c7-5a94-4e6d-81d1-80f26f7047ec",
  "date_created": "2026-03-02T18:02:27.340000Z",
  "date_modified": "2026-03-02T18:02:27.340000Z",
  "file_hash": "2a54d22dd1205587fee5fddcbfeb686b4b61595c2caff81d71f1bdecc8156074",
  "private": false,
  "record": {
    "abstract": "Any positive-energy state of a free Dirac particle that is initially\nhighly-localized, evolves in time by spreading at speeds close to the speed of\nlight. This general phenomenon is explained by the fact that the Dirac\nevolution can be approximated arbitrarily closely by a quantum random walk,\nwhere the roles of coin and walker systems are naturally attributed to the spin\nand position degrees of freedom of the particle. Initially entangled and\nspatially localized spin-position states evolve with asymptotic two-horned\ndistributions of the position probability, familiar from earlier studies of\nquantum walks. For the Dirac particle, the two horns travel apart at close to\nthe speed of light.",
    "arxiv_id": "quant-ph/0605195",
    "authors": [
      "A. J. Bracken",
      "D. Ellinas",
      "I. Smyrnakis"
    ],
    "categories": [
      "quant-ph"
    ],
    "doi": "10.1103/PhysRevA.75.022322",
    "title": "Free Dirac evolution as a quantum random walk",
    "url": "https://arxiv.org/abs/quant-ph/0605195"
  },
  "schema_id": "dorsal/arxiv",
  "source": {
    "execution_id": "0c356172-9832-4b70-be74-a449aa1239a5",
    "id": "arXiv Dataset IDs",
    "type": "Model",
    "variant": "snapshot-2026-03-01",
    "version": "0.1.0"
  },
  "user_id": 1000002
}