{
  "annotation_id": "00c72e39-dcec-49d4-a29c-1ff24e630835",
  "date_created": "2026-03-02T18:01:52.563000Z",
  "date_modified": "2026-03-02T18:01:52.563000Z",
  "file_hash": "94b6705b0b4954c3e808f60e003fb159eac9b858900ca9c273bdc882c24bc98b",
  "private": false,
  "record": {
    "abstract": "The relative entropy description of Holevo-Schumacher-Westmoreland (HSW)\nclassical channel capacity is applied to single qubit channels. A simple\nformula for the relative entropy of qubit density matrices in the Bloch sphere\nrepresentation is derived. This formula is combined with the\nKing-Ruskai-Szarek-Werner qubit channel ellipsoid picture to analyze several\nunital and non-unital qubit channels in detail. An alternate proof that the\noptimal HSW signalling states for single qubit unital channels are those states\nwith the minimum channel output entropy is presented. The derivation is based\non the symmetries of the qubit relative entropy formula and the\nKing-Ruskai-Szarek-Werner qubit channel ellipsoid picture. A proof is given\nthat the average output density matrix of any set of optimal HSW signalling\nstates for a (qubit or non-qubit) quantum channel is unique.",
    "arxiv_id": "quant-ph/0207128",
    "authors": [
      "John Cortese"
    ],
    "categories": [
      "quant-ph"
    ],
    "title": "Relative Entropy and Single Qubit Holevo-Schumacher-Westmoreland Channel   Capacity",
    "url": "https://arxiv.org/abs/quant-ph/0207128"
  },
  "schema_id": "dorsal/arxiv",
  "source": {
    "execution_id": "13aba755-26c2-4181-9559-4971476e0536",
    "id": "arXiv Dataset IDs",
    "type": "Model",
    "variant": "snapshot-2026-03-01",
    "version": "0.1.0"
  },
  "user_id": 1000002
}