{
  "annotation_id": "a4bf052b-aed2-4718-9095-50cb78cba3df",
  "date_created": "2026-03-02T18:02:23.965000Z",
  "date_modified": "2026-03-02T18:02:23.965000Z",
  "file_hash": "5475cade8340f99323782acd3cd0b64a68a44eb603c63d84c6a2dfebdf140f8f",
  "private": false,
  "record": {
    "abstract": "We show that there exists a gap between the performance of separable and\ncollective measurements in qubit mixed-state estimation that persists in the\nlarge sample limit. We characterize such gap in terms of the corresponding\nbounds on the mean fidelity. We present an adaptive protocol that attains the\nseparable-measurement bound. This (optimal separable) protocol uses von Neumann\nmeasurements and can be easily implemented with current technology.",
    "arxiv_id": "quant-ph/0512177",
    "authors": [
      "E. Bagan",
      "M. A. Ballester",
      "R. D. Gill",
      "R. Munoz-Tapia",
      "O. Romero-Isart"
    ],
    "categories": [
      "quant-ph"
    ],
    "doi": "10.1103/PhysRevLett.97.130501",
    "journal_ref": "Phys. Rev. Lett. 97, 130501 (2006)",
    "title": "Separable Measurement Estimation of Density Matrices and its Fidelity   Gap with Collective Protocols",
    "url": "https://arxiv.org/abs/quant-ph/0512177"
  },
  "schema_id": "dorsal/arxiv",
  "source": {
    "execution_id": "98e0f985-7dbe-4d65-ac4e-d02a7cd496a7",
    "id": "arXiv Dataset IDs",
    "type": "Model",
    "variant": "snapshot-2026-03-01",
    "version": "0.1.0"
  },
  "user_id": 1000002
}