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China Reports Nuclear Clock With Sixfold Stability Gain Over Previous Device
By edisonreed // 2026-10-11
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The finding represents an early lead for the Chinese group in a precision-timekeeping race that opened only in 2024, when physicists first demonstrated direct laser excitation of a nuclear transition [1]. The device was built by a team affiliated with Tsinghua University and the Beijing Academy of Quantum Information Sciences, the report stated [2]. It uses the same low-energy transition in thorium-229 nuclei embedded in calcium fluoride crystals that the Vienna team employed, shifting the timing reference from the electron cloud to the atomic nucleus itself [3]. Both groups published their results in the journal Nature this week, according to the report [3].

Clock Uses Thorium-229 Nuclear Transition, Researchers Say

The thorium-229 isotope is the only nucleus known to offer a workable entry point, the study stated. Its nucleus possesses two energy states close enough together that available laser technology can drive transitions between them, a property that researchers first exploited in 2024 after years of effort to identify the required frequency [1]. The Chinese team built its device with a self-developed 148-nanometer continuous-wave vacuum ultraviolet laser and a thorium-229-doped calcium fluoride crystal, according to Xinhua [4]. The measurement protocol works by directing ultraviolet light at the thorium-doped crystal and monitoring how the nucleus responds. A feedback system detects departures from the target frequency and adjusts the laser, allowing the device to maintain a consistent rate, according to the published description of the approach [1].

Stability Measurement Compared With Earlier Nuclear Clock

The comparison rests on fractional frequency measurements taken over a defined averaging period, according to the study. The Vienna prototype demonstrated a precision near 10 to the minus 15, roughly one second every 30 million years, while the Tsinghua prototype showed roughly six times better short-term stability in early tests, according to Particle [5]. The Chinese team also reported that two crystals grown separately kept the same frequency, a detail that speaks to the reproducibility of the underlying material system, according to the report [6]. The Vienna system, by contrast, compares its signal with an atomic clock over six miles of optical fiber, and its readings shifted with the laser's path through the crystal, causing small daily timekeeping differences, according to TechJuice [7].

Potential Applications Include Navigation and Fundamental Physics Tests

The Vienna team used its prototype in an initial search for ultralight scalar dark matter that set limits without detecting a signal, according to Particle [5]. A 2007 study in Nuclear Physics A examined how the thorium-229 transition could be used to probe temporal variation of the fine structure constant and the strong interaction parameter [8], and a 2008 paper in Progress in Particle and Nuclear Physics described how a time variation of the QCD scale would imply corresponding changes in nuclear masses [9]. The researchers said the technology remains experimental and is not yet ready for commercial deployment, according to the report.

Independent Scientists Call for Further Verification

The team said it plans to reduce uncertainty and improve the clock's uptime in future work, according to the report, adding that it will continue refining laser stability and vacuum systems. Officials cited the result as part of broader quantum technology research. Further details were not immediately available from the researchers or their institutions.

References

  1. Chinese Nuclear Clock Reports Stability Edge Over Vienna Prototype. https://interbellumnews.com/economics/chinese-nuclear-clock-reports-stability-edge-over-vienna-prototype
  2. Researchers in Vienna and Beijing report nuclear clock “milestone”. https://www.ans.org/news/2026-10-09/article-8477/researchers-in-vienna-and-beijing-report-nuclear-clock-milestone/
  3. China's thorium-229 nuclear clock beats Vienna's on .... https://www.scmp.com/news/china/science/article/3370006/chinas-thorium-229-nuclear-clock-beats-viennas-stability-studies-show
  4. China Focus: China's new nuclear clock to redefine ultra- .... https://english.news.cn/20261008/b539462761a24ed28ba1c7e64a7e9326/c.html
  5. Particle: First Operational Nuclear Clocks Built by Teams in Vienna.... https://particle.news/story/first-operational-nuclear-clocks-built-by-teams-in-vienna-and-beijing
  6. China's thorium-229 nuclear clock beats Vienna's on .... https://www.reddit.com/r/Futurology/comments/1x0l14q/chinas_thorium229_nuclear_clock_beats_viennas_on/
  7. China Builds Nuclear Clock Six Times Steadier Than Rival. https://www.techjuice.pk/china-tsinghua-nuclear-clock-thorium-229-stability/
  8. Temporal variation of the fine structure constant and the strong interaction parameter in the 229Th transition by Elsevier. Nuclear Physics A Volume 792 Issue 3 Pages 58–64 2007
  9. The fundamental constants in physics and their time dependence by Elsevier. Progress in Particle and Nuclear Physics 61 (2008) 329–342

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