{
  "annotation_id": "6edbd8e9-4040-4b3d-9e72-0fdeb3b903aa",
  "date_created": "2026-03-02T18:02:27.564000Z",
  "date_modified": "2026-03-02T18:02:27.564000Z",
  "file_hash": "eb26d6f845641e95a4ef5f06642ee41830e29f7fa6d45d0beafb24fcbb310be5",
  "private": false,
  "record": {
    "abstract": "An (n,1,p)-Quantum Random Access (QRA) coding, introduced by Ambainis, Nayak,\nTa-shma and Vazirani in ACM Symp. on Theory of Computing 1999, is the following\ncommunication system: The sender which has n-bit information encodes his/her\ninformation into one qubit, which is sent to the receiver. The receiver can\nrecover any one bit of the original n bits correctly with probability at least\np, through a certain decoding process based on positive operator-valued\nmeasures. Actually, Ambainis et al. shows the existence of a (2,1,0.85)-QRA\ncoding and also proves the impossibility of its classical counterpart. Chuang\nimmediately extends it to a (3,1,0.79)-QRA coding and whether or not a\n(4,1,p)-QRA coding such that p \u003e 1/2 exists has been open since then. This\npaper gives a negative answer to this open question.",
    "arxiv_id": "quant-ph/0604061",
    "authors": [
      "Masahito Hayashi",
      "Kazuo Iwama",
      "Harumichi Nishimura",
      "Rudy Raymond",
      "Shigeru Yamashita"
    ],
    "categories": [
      "quant-ph"
    ],
    "doi": "10.1088/1367-2630/8/8/129",
    "journal_ref": "New J. Phys 8 (2006) 129",
    "title": "(4,1)-Quantum Random Access Coding Does Not Exist",
    "url": "https://arxiv.org/abs/quant-ph/0604061"
  },
  "schema_id": "dorsal/arxiv",
  "source": {
    "execution_id": "c4c03717-746e-4676-94e3-4bd7d8e9cc66",
    "id": "arXiv Dataset IDs",
    "type": "Model",
    "variant": "snapshot-2026-03-01",
    "version": "0.1.0"
  },
  "user_id": 1000002
}