{
  "annotation_id": "ace112b2-b533-4ca6-a950-7ea0a43e87c9",
  "date_created": "2026-03-02T18:02:16.670000Z",
  "date_modified": "2026-03-02T18:02:16.670000Z",
  "file_hash": "a39ec3f179b26aeda9df5fd92e687192db230b0fb4bc7b5f285e4a9b35fec86a",
  "private": false,
  "record": {
    "abstract": "We introduce methods for clock synchronization that make use of the adiabatic\nexchange of nondegenerate two-level quantum systems: ticking qubits. Schemes\ninvolving the exchange of N independent qubits with frequency $\\omega$ give a\nsynchronization accuracy that scales as $(\\omega\\sqrt{N})^{-1}$, i.e., as the\nstandard quantum limit. We introduce a protocol that makes use of N coherent\nexchanges of a single qubit at frequency $\\omega$, leading to an accuracy that\nscales as $(\\omega N)^{-1}\\log N$. This protocol beats the standard quantum\nlimit without the use of entanglement, and we argue that this scaling is the\nfundamental limit for clock synchronization allowed by quantum mechanics. We\nanalyse the performance of these protocols when used with a lossy channel.",
    "arxiv_id": "quant-ph/0505112",
    "authors": [
      "Mark de Burgh",
      "Stephen D. Bartlett"
    ],
    "categories": [
      "quant-ph"
    ],
    "doi": "10.1103/PhysRevA.72.042301",
    "journal_ref": "Phys. Rev. A, 72, 042301 (2005)",
    "title": "Quantum methods for clock synchronization: Beating the standard quantum   limit without entanglement",
    "url": "https://arxiv.org/abs/quant-ph/0505112"
  },
  "schema_id": "dorsal/arxiv",
  "source": {
    "execution_id": "a9542b77-279f-48c1-8132-9da740baf893",
    "id": "arXiv Dataset IDs",
    "type": "Model",
    "variant": "snapshot-2026-03-01",
    "version": "0.1.0"
  },
  "user_id": 1000002
}