{
  "annotation_id": "e8a963fd-25cf-4403-8b73-3d21fdf53894",
  "date_created": "2026-03-02T18:02:27.625000Z",
  "date_modified": "2026-03-02T18:02:27.625000Z",
  "file_hash": "4e426e4c81cf6e9fecd3876ec9c42a6287a1480eff735dd7276ae07733a85aca",
  "private": false,
  "record": {
    "abstract": "We present a simple method to obtain an upper bound on the achievable secret\nkey rate in quantum key distribution (QKD) protocols that use only\nunidirectional classical communication during the public-discussion phase. This\nmethod is based on a necessary precondition for one-way secret key\ndistillation; the legitimate users need to prove that there exists no quantum\nstate having a symmetric extension that is compatible with the available\nmeasurements results. The main advantage of the obtained upper bound is that it\ncan be formulated as a semidefinite program, which can be efficiently solved.\nWe illustrate our results by analysing two well-known qubit-based QKD\nprotocols: the four-state protocol and the six-state protocol. Recent results\nby Renner et al., Phys. Rev. A 72, 012332 (2005), also show that the given\nprecondition is only necessary but not sufficient for unidirectional secret key\ndistillation.",
    "arxiv_id": "quant-ph/0603270",
    "authors": [
      "Tobias Moroder",
      "Marcos Curty",
      "Norbert L\u00fctkenhaus"
    ],
    "categories": [
      "quant-ph"
    ],
    "doi": "10.1103/PhysRevA.74.052301",
    "journal_ref": "Phys. Rev. A 74, 052301 (2006)",
    "title": "One-way quantum key distribution: Simple upper bound on the secret key   rate",
    "url": "https://arxiv.org/abs/quant-ph/0603270"
  },
  "schema_id": "dorsal/arxiv",
  "source": {
    "execution_id": "50b4409e-cd52-48b6-9f45-ce958e39c1ab",
    "id": "arXiv Dataset IDs",
    "type": "Model",
    "variant": "snapshot-2026-03-01",
    "version": "0.1.0"
  },
  "user_id": 1000002
}