VIENNA, October 7 — The shift is here: nuclear timekeeping has moved from theory to working hardware, with independent teams in Vienna and Beijing unveiling the world’s first two operating nuclear clocks based on thorium-229 nuclei. Published in Nature on October 7, 2026, the breakthrough marks a transition from atomic clocks that rely on electron shell transitions to nuclear clocks that harness the far more stable oscillations within the thorium-229 nucleus. The Vienna team, led by physicist Thorsten Schumm at TU Wien, has pursued this goal since 2008.
Their prototype uses thorium-229 nuclei embedded in calcium fluoride crystals, benefiting from what they describe as superior crystal quality — higher thorium concentration and better optical properties. This approach yields a stability performance of losing approximately one second every few million years, a level of precision that already surpasses many conventional systems.
In contrast, the Beijing team, led by physicist Shiqian Ding at Tsinghua University, entered the field later but achieved rapid progress through a stronger, more powerful laser system. Their setup emphasizes highly stabilized timekeeping loops and rapid nuclear oscillation, resulting in a thorium-229 nuclear clock roughly six times more stable than Vienna’s — meaning it would lose about two seconds over 65 million years. Both teams independently validated the robustness of the nuclear clock concept using their distinct methods, proving the feasibility of the technology across different engineering paths.
Now, the groups are exploring collaboration to combine Vienna’s high-quality thorium-doped crystals with Beijing’s advanced laser technology. The goal is to build a unified nuclear clock that could surpass the performance of today’s best atomic clocks, potentially redefining standards for navigation, telecommunications, and fundamental physics research.
What’s changing is not just precision but the very foundation of timekeeping — moving from electron-based transitions to nuclear resonances that are far less susceptible to external disturbances. Watch this space: as these prototypes mature, nuclear clocks may soon transition from laboratory curiosities to practical tools embedded in global timing networks, opening new avenues for testing relativity, detecting dark matter, and probing the constancy of fundamental constants.
