{
  "annotation_id": "e01336fe-d36c-44a4-ae6e-4c5f25e7618d",
  "date_created": "2026-03-02T18:02:06.581000Z",
  "date_modified": "2026-03-02T18:02:06.581000Z",
  "file_hash": "61095bc51071e7fc121c9d0a96a885e34a5d89b1fab9890f93b7a6803045c7da",
  "private": false,
  "record": {
    "abstract": "We derive an exact expression for the quantumness of a Hilbert space (defined\nin quant-ph/0302092), and show that in composite Hilbert spaces the signal\nstates must contain at least some entangled states in order to achieve such a\nsensitivity. Furthermore, we establish that the accessible fidelity for\nsymmetric informationally complete signal ensembles is equal to the\nquantumness. Though spelling the most trouble for an eavesdropper because of\nthis, it turns out that the accessible fidelity is nevertheless easy for her to\nachieve in this case: Any measurement consisting of rank-one POVM elements is\nan optimal measurement, and the simple procedure of reproducing the projector\nassociated with the measurement outcome is an optimal output strategy. Two and\nepsilon elevator stories are added for entertainment.",
    "arxiv_id": "quant-ph/0404122",
    "authors": [
      "Christopher A. Fuchs"
    ],
    "categories": [
      "quant-ph"
    ],
    "title": "On the Quantumness of a Hilbert Space",
    "url": "https://arxiv.org/abs/quant-ph/0404122"
  },
  "schema_id": "dorsal/arxiv",
  "source": {
    "execution_id": "0fc3be5c-5f3d-4c64-a088-d5aa888396e9",
    "id": "arXiv Dataset IDs",
    "type": "Model",
    "variant": "snapshot-2026-03-01",
    "version": "0.1.0"
  },
  "user_id": 1000002
}