Overview
- On Wednesday, October 7, 2026, independent teams in Vienna (PTB–TU Wien) and Beijing (Tsinghua) published Nature papers reporting the first operational nuclear clocks.
- Both prototypes use thorium-229 doped into calcium fluoride crystals and are interrogated with narrow-linewidth continuous-wave ultraviolet lasers to drive a nuclear transition rather than an electronic one.
- The Vienna device demonstrated a precision near 1×10⁻15 and was used to set new limits on ultralight dark-matter couplings, while the Beijing device showed lower short-term fractional instability (about 5×10⁻13/√τ) thanks to stronger laser interrogation.
- Researchers say neither prototype yet outperforms the best optical atomic clocks and that clear technical paths to better performance include more powerful and narrower lasers, improved host crystals and dopant control, and trapped-ion thorium implementations.
- Beyond timekeeping, nuclear clocks could shrink and harden precision timing for navigation and surveying and provide a sensitive new probe of fundamental physics because thorium-229 offers the rare low-energy nuclear transition that lasers can address.