Overview
- Two independent research groups in Vienna and at Tsinghua University posted arXiv preprints Monday describing functioning nuclear clocks that lock laser frequencies to a low‑energy thorium‑229 nuclear transition inside calcium fluoride crystals.
- The Vienna team ran its system as a standalone clock, compared its output to an established ytterbium‑ion atomic clock, operated at room temperature, and used the device in an initial search for ultralight dark matter with no signal found.
- The Tsinghua team focused on reproducibility and measured nearly identical frequencies from two separately produced crystals, addressing a key concern for solid‑state clock repeatability.
- These prototypes do not yet beat the best atomic clocks but show clear routes to faster gains through better vacuum‑ultraviolet lasers, improved crystals, and upgraded electronics that could raise stability in the coming years.
- If developed further, the solid‑state approach could make precise timekeepers smaller and more robust for satellite navigation, communications, geodetic mapping and new laboratory tests of fundamental constants, with peer review of the current results still pending.