{
  "abstract": "Redefining the International system of Units (SI) second requires independent frequency-ratio measurements between clocks based on different laboratories, with an overall uncertainty below 5E-18, to validate individual clock evaluations through consistency checks. Reaching this uncertainty over long distances has remained challenging. So far, comparisons at this level have been achieved only a few times, between co-located clocks, and their results disagree markedly. Previous high-precision comparisons have therefore been limited to local or kilometre-scale links. Here we compare a ytterbium optical lattice clock in Wuhan with a strontium optical lattice clock in Shanghai over a phase-stabilized fiber link spanning 1350 km, and determine the Yb/Sr frequency ratio to be 1.207 507 039 343 337 716 0(26), with a Bayesian statistical uncertainty of 1.14E-18 and a total uncertainty of 2.18E-18. To our knowledge, this is the first intercity long distance frequency-ratio measurement, whose total uncertainty reaches the level required by the redefinition roadmap. The measured ratio exhibits a significant correlation with Earth tides and its response agree with the model within the statistical uncertainty. At intercity scale, this comparison demonstrates the capability of an optical-clock network for frequency comparison and Earths gravitational-potential sensing, a key step toward a wide-area optical-clock network.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2610.34250",
  "author_total": 35,
  "authors": [
    {
      "name": "Lei Hou"
    },
    {
      "name": "Xiang-Pei Liu"
    },
    {
      "name": "Zhuan-Xian Xiong"
    },
    {
      "name": "Fa-Xi Chen"
    },
    {
      "name": "Wen-Xuan Song"
    },
    {
      "name": "Jian-Yu Guan"
    },
    {
      "name": "Qiang Zhu"
    },
    {
      "name": "Yu-Chen Zhang"
    },
    {
      "name": "Xiang Zhang"
    },
    {
      "name": "Bing Wang"
    },
    {
      "name": "De-Zhi Xiong"
    },
    {
      "name": "De-Quan Kong"
    },
    {
      "name": "Jia-Hao Zhang"
    },
    {
      "name": "Long-Fei Liao"
    },
    {
      "name": "Shao-Mao Wang"
    },
    {
      "name": "Xing-Yang Cui"
    },
    {
      "name": "Ping Xu"
    },
    {
      "name": "Peng Liu"
    },
    {
      "name": "Jie Li"
    },
    {
      "name": "Xiao Jiang"
    },
    {
      "name": "Ling-Xiang He"
    },
    {
      "name": "Li-Bo Li"
    },
    {
      "name": "Qi Shen"
    },
    {
      "name": "Youchao Xie"
    },
    {
      "name": "Lei Wang"
    },
    {
      "name": "Sheng-Kai Liao"
    },
    {
      "name": "Juan Yin"
    },
    {
      "name": "Cheng-Zhi Peng"
    },
    {
      "name": "Wen-Bin Shen"
    },
    {
      "name": "Bao-Long Lu"
    },
    {
      "name": "Han-Ning Dai"
    },
    {
      "name": "Yu-Ao Chen"
    },
    {
      "name": "Qiang Zhang"
    },
    {
      "name": "Hai-Feng Jiang"
    },
    {
      "name": "Jian-Wei Pan"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/bd03jydqy7zm7.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2610.34250",
  "fulltext_url": null,
  "id": "bd03jydqy7zm7",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2610.34250",
  "language": null,
  "licence": "LicenseRef-arXiv-nonexclusive-1.0",
  "licence_label": "arXiv licence",
  "licence_source": "article",
  "licence_url": "http://arxiv.org/licenses/nonexclusive-distrib/1.0/",
  "metadata_licence": "CC0-1.0",
  "native_subjects": [
    [
      "arxiv",
      "physics.atom-ph"
    ],
    [
      "arxiv",
      "physics.optics"
    ],
    [
      "openalex",
      "3107|Advanced Frequency and Time Standards"
    ]
  ],
  "openalex": "W7223820958",
  "pdf_url": "https://arxiv.org/pdf/2610.34250",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-25",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/bd03jydqy7zm7.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:35:35Z",
      "native_id": "2610.34250",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2610.34250"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "arxiv:physics.atom-ph",
      "subfield": "amo"
    },
    {
      "field": "physics",
      "origin": "arxiv:physics.optics",
      "subfield": "optics-photonics"
    }
  ],
  "title": "Yb/Sr optical clock comparison at 2.2E-18 uncertainty over a 1350-km fiber link",
  "title_text": "Yb/Sr optical clock comparison at 2.2E-18 uncertainty over a 1350-km fiber link",
  "type": "preprint",
  "updated_at": "2026-10-30T12:35:35Z",
  "url": "https://research.draconitic.com/paper/bd03jydqy7zm7",
  "venue": "arXiv",
  "versions": []
}