{
  "annotation_id": "11d85b2b-bf38-4369-855d-dfa247c5e215",
  "date_created": "2026-03-02T18:01:59.934000Z",
  "date_modified": "2026-03-02T18:01:59.934000Z",
  "file_hash": "2aa0ca3122658b9e0063ad88496e9c6339716426dc2c49edbe6d6fbb9e844ace",
  "private": false,
  "record": {
    "abstract": "For one qubit systems, we present a short, elementary argument characterizing\nunital quantum operators in terms of their action on Bloch vectors. We then\nshow how our approach generalizes to multi-qubit systems, obtaining\ninequalities that govern when a ``diagonal\u0027\u0027 superoperator on the Bloch region\nis a quantum operator. These inequalities are the n-qubit analogue of the\nAlgoet-Fujiwara conditions. Our work is facilitated by an analysis of\noperator-sum decompositions in which negative summands are allowed.",
    "arxiv_id": "quant-ph/0308089",
    "authors": [
      "P. S. Bourdon",
      "H. T. Williams"
    ],
    "categories": [
      "quant-ph"
    ],
    "doi": "10.1103/PhysRevA.69.022314",
    "title": "Unital quantum operators on the Bloch ball and Bloch region",
    "url": "https://arxiv.org/abs/quant-ph/0308089"
  },
  "schema_id": "dorsal/arxiv",
  "source": {
    "execution_id": "18e22122-3d3a-4435-940a-7a81e8d13174",
    "id": "arXiv Dataset IDs",
    "type": "Model",
    "variant": "snapshot-2026-03-01",
    "version": "0.1.0"
  },
  "user_id": 1000002
}