{
  "annotation_id": "7763d8ad-ac41-4edf-8854-8112f9115866",
  "date_created": "2026-03-02T18:02:17.214000Z",
  "date_modified": "2026-03-02T18:02:17.214000Z",
  "file_hash": "c09f2605b6032fce62219b034390421fed05ec173f410e02fb07fd3929724cd2",
  "private": false,
  "record": {
    "abstract": "In order to make a unified treatment for estimation problems of a very small\nnoise or a very weak signal in a quantum process, we introduce the notion of a\nlow-noise quantum channel with one noise parameter. It is known in several\nexamples that prior entanglement together with nonlocal output measurement\nimproves the performance of the channel estimation. In this paper, we study\nthis ``ancilla-assisted enhancement\u0027\u0027 for estimation of the noise parameter in\na general low-noise channel. For channels on two level systems we prove that\nthe enhancement factor, the ratio of the Fisher information of the\nancilla-assisted estimation to that of the original one, is always upper\nbounded by 3/2. Some conditions for the attainability are also given with\nillustrative examples.",
    "arxiv_id": "quant-ph/0507055",
    "authors": [
      "Masahiro Hotta",
      "Tokishiro Karasawa",
      "Masanao Ozawa"
    ],
    "categories": [
      "quant-ph"
    ],
    "doi": "10.1103/PhysRevA.72.052334",
    "journal_ref": "Phys. Rev. A 72, 052334 (11) (2005)",
    "title": "Ancilla-Assisted Enhancement of Channel Estimation for Low-Noise   Parameters",
    "url": "https://arxiv.org/abs/quant-ph/0507055"
  },
  "schema_id": "dorsal/arxiv",
  "source": {
    "execution_id": "aae1aa6c-0c8f-4af8-8c29-a382f81398b3",
    "id": "arXiv Dataset IDs",
    "type": "Model",
    "variant": "snapshot-2026-03-01",
    "version": "0.1.0"
  },
  "user_id": 1000002
}