{
  "annotation_id": "9d60f6ec-b7a1-4b64-b7bd-4e675a219c3a",
  "date_created": "2026-03-02T18:02:16.361000Z",
  "date_modified": "2026-03-02T18:02:16.361000Z",
  "file_hash": "f007b5cacbe15d10dbe11603d9091613a4e4c530f40ca850b1b624b356490fcf",
  "private": false,
  "record": {
    "abstract": "Even though the time-reversal is unphysical (it corresponds to the complex\nconjugation of the density matrix), for some restricted set of states it can be\nachieved unitarily, typically when there is a common de-phasing in a n-level\nsystem. However, in the presence of multiple phases (i. e. a different\nde-phasing for each element of an orthogonal basis occurs) the time reversal is\nno longer physically possible. In this paper we derive the channel which\noptimally approaches in fidelity the time-reversal of multi-phase equatorial\nstates in arbitrary (finite) dimension. We show that, in contrast to the\ncustomary case of the Universal-NOT on qubits (or the universal conjugation in\narbitrary dimension), the optimal phase covariant time-reversal for equatorial\nstates is a nonclassical channel, which cannot be achieved via a\nmeasurement/preparation procedure. Unitary realizations of the optimal\ntime-reversal channel are given with minimal ancillary dimension, exploiting\nthe simplex structure of the optimal maps.",
    "arxiv_id": "quant-ph/0504016",
    "authors": [
      "Francesco Buscemi",
      "Giacomo Mauro D\u0027Ariano",
      "Chiara Macchiavello"
    ],
    "categories": [
      "quant-ph"
    ],
    "doi": "10.1103/PhysRevA.72.062311",
    "journal_ref": "Phys. Rev. A 72, 062311 (2005) [5 pages]",
    "title": "Optimal Time-Reversal of Multi-phase Equatorial States",
    "url": "https://arxiv.org/abs/quant-ph/0504016"
  },
  "schema_id": "dorsal/arxiv",
  "source": {
    "execution_id": "7c11b56b-e28a-4e3f-9d40-f49a8d91c894",
    "id": "arXiv Dataset IDs",
    "type": "Model",
    "variant": "snapshot-2026-03-01",
    "version": "0.1.0"
  },
  "user_id": 1000002
}