{
  "annotation_id": "8d7bb6d4-8a1d-4e91-ada2-81a5c6f42d2a",
  "date_created": "2026-03-02T18:02:33.643000Z",
  "date_modified": "2026-03-02T18:02:33.643000Z",
  "file_hash": "e45baa8bc80d327dfd010b3564dae893d94fa002c8bbe1642ca14b3fc72ece1a",
  "private": false,
  "record": {
    "abstract": "For a massive spin 1/2 field, we present the reduced spin and helicity\ndensity matrix, respectively, for the same pure one particle state. Their\nrelation has also been developed. Furthermore, we calculate and compare the\ncorresponding entanglement entropy for spin and helicity within the same\ninertial reference frame. Due to the distinct dependence on momentum degree of\nfreedom between spin and helicity states, the resultant helicity entropy is\ndifferent from that of spin in general. In particular, we find that both\nhelicity entanglement for a spin eigenstate and spin entanglement for a right\nhanded or left handed helicity state do not vanish and their Von Neumann\nentropy has no dependence on the specific form of momentum distribution as long\nas it is isotropic.",
    "arxiv_id": "quant-ph/0702028",
    "authors": [
      "Song He",
      "Shuxin Shao",
      "Hongbao Zhang"
    ],
    "categories": [
      "quant-ph",
      "hep-th"
    ],
    "doi": "10.1142/S0219749908003360",
    "journal_ref": "Int.J.Quant.Inf.6:181,2008",
    "title": "Entanglement Entropy: Helicity versus Spin",
    "url": "https://arxiv.org/abs/quant-ph/0702028"
  },
  "schema_id": "dorsal/arxiv",
  "source": {
    "execution_id": "b052c643-cf5f-4317-8786-8f0300792e53",
    "id": "arXiv Dataset IDs",
    "type": "Model",
    "variant": "snapshot-2026-03-01",
    "version": "0.1.0"
  },
  "user_id": 1000002
}