Scientists in Austria and China have independently built the world's first operating nuclear clocks, a breakthrough reported in two papers published in the journal Nature on October 7. The devices keep time using transitions inside the atomic nucleus rather than the electron shells used by today's atomic clocks — a feat physicists have chased for decades.
A clock that stabilises itself
The Vienna team, led by Thorsten Schumm at TU Wien together with Ekkehard Peik at Germany's PTB metrology institute in Braunschweig, demonstrated the world's first self-stabilising, stand-alone nuclear clock. The system remained stable for more than 24 hours without any intervention, TU Wien reported. The breakthrough follows the team's earlier milestones: in April 2024 they first excited thorium nuclei with laser beams, and later that year they coupled a thorium apparatus to a conventional optical atomic clock.
The heart of the device is a crystal containing thorium-229 atoms, produced at TU Wien, which is irradiated with a laser. The laser can switch the thorium nucleus between two energy states whose energies lie extremely close together — a property almost unique to this isotope, since other nuclei have energy gaps far too large for laser light to bridge.
"What you really want is a self-stabilizing nuclear clock," Schumm explained. "The basic idea is simple: you have a laser and you have thorium. The laser changes the energy state of the thorium nuclei, and the thorium nuclei are used to stabilize the frequency of the laser." Because the nuclei absorb the laser light only when its frequency is exactly right, any drift is detected and automatically corrected — the same feedback principle that conventional atomic clocks use.
Not yet record-breaking — but a new era
The new clock's precision was measured over a day at roughly 10 to the power of minus 15 — an error of about one second in 30 million years. "This is not yet at the level of the world's best optical atomic clocks, but for a first prototype it is a fantastic result," Schumm said. The team plans to improve precision with stronger lasers and better thorium crystals.
The promise lies in the physics: atomic nuclei are more than 10,000 times smaller than atoms and react far more weakly to external disturbances, making them potentially much more reliable timekeepers. The achievement could open a new chapter in precision timekeeping and give physicists a powerful new way to probe the fundamental laws of nature.
Sources:
Phys.org: The first stand-alone nuclear clock is ticking in Vienna
Kashmir Reader: Scientists build world's first operating nuclear clocks
A clock that stabilises itself
The Vienna team, led by Thorsten Schumm at TU Wien together with Ekkehard Peik at Germany's PTB metrology institute in Braunschweig, demonstrated the world's first self-stabilising, stand-alone nuclear clock. The system remained stable for more than 24 hours without any intervention, TU Wien reported. The breakthrough follows the team's earlier milestones: in April 2024 they first excited thorium nuclei with laser beams, and later that year they coupled a thorium apparatus to a conventional optical atomic clock.
The heart of the device is a crystal containing thorium-229 atoms, produced at TU Wien, which is irradiated with a laser. The laser can switch the thorium nucleus between two energy states whose energies lie extremely close together — a property almost unique to this isotope, since other nuclei have energy gaps far too large for laser light to bridge.
"What you really want is a self-stabilizing nuclear clock," Schumm explained. "The basic idea is simple: you have a laser and you have thorium. The laser changes the energy state of the thorium nuclei, and the thorium nuclei are used to stabilize the frequency of the laser." Because the nuclei absorb the laser light only when its frequency is exactly right, any drift is detected and automatically corrected — the same feedback principle that conventional atomic clocks use.
Not yet record-breaking — but a new era
The new clock's precision was measured over a day at roughly 10 to the power of minus 15 — an error of about one second in 30 million years. "This is not yet at the level of the world's best optical atomic clocks, but for a first prototype it is a fantastic result," Schumm said. The team plans to improve precision with stronger lasers and better thorium crystals.
The promise lies in the physics: atomic nuclei are more than 10,000 times smaller than atoms and react far more weakly to external disturbances, making them potentially much more reliable timekeepers. The achievement could open a new chapter in precision timekeeping and give physicists a powerful new way to probe the fundamental laws of nature.
Sources:
Phys.org: The first stand-alone nuclear clock is ticking in Vienna
Kashmir Reader: Scientists build world's first operating nuclear clocks
