{
  "annotation_id": "c804a862-1eed-48b6-914e-3e84bc520d76",
  "date_created": "2026-03-02T18:02:16.787000Z",
  "date_modified": "2026-03-02T18:02:16.787000Z",
  "file_hash": "1bff4bc3066db6ac323ef8baa5adbd8fc32f8697ad110c8d0b3d85d29ad33bba",
  "private": false,
  "record": {
    "abstract": "We investigate the problem of cloning a set of states that is invariant under\nthe action of an irreducible group representation. We then characterize the\ncloners that are \"extremal\" in the convex set of group covariant cloning\nmachines, among which one can restrict the search for optimal cloners. For a\nset of states that is invariant under the discrete Weyl-Heisenberg group, we\nshow that all extremal cloners can be unitarily realized using the so-called\n\"double-Bell states\", whence providing a general proof of the popular ansatz\nused in the literature for finding optimal cloners in a variety of settings.\nOur result can also be generalized to continuous-variable optimal cloning in\ninfinite dimensions, where the covariance group is the customary\nWeyl-Heisenberg group of displacements.",
    "arxiv_id": "quant-ph/0507130",
    "authors": [
      "G. Chiribella",
      "G. M. D\u0027Ariano",
      "P. Perinotti",
      "N. J. Cerf"
    ],
    "categories": [
      "quant-ph"
    ],
    "doi": "10.1103/PhysRevA.72.042336",
    "journal_ref": "Phys. Rev. A 72 042336 (2005)",
    "title": "Extremal quantum cloning machines",
    "url": "https://arxiv.org/abs/quant-ph/0507130"
  },
  "schema_id": "dorsal/arxiv",
  "source": {
    "execution_id": "69b2e0c1-e357-43b8-94bb-877b6f338f1c",
    "id": "arXiv Dataset IDs",
    "type": "Model",
    "variant": "snapshot-2026-03-01",
    "version": "0.1.0"
  },
  "user_id": 1000002
}