Physicists have created working nuclear clocks for the first time

Physicists from Europe and China have independently created the world's first working nuclear clocks — devices that measure time based on oscillations of an atomic nucleus rather than electrons. The development could lead to clocks that surpass modern atomic standards in accuracy and also open new possibilities for searching for dark matter and testing fundamental laws of physics. A preprint of the work has been published on the arXiv portal.

To date, the most accurate instruments for measuring time remain atomic clocks. Their operation is based on transitions of electrons between energy levels within atoms. The precision of these devices is staggering: they are capable of drifting by less than one second over billions of years.

But scientists have long suspected that atomic nuclei could serve as an even more reliable time standard. Unlike electrons, which are located on the outer shells of an atom and are sensitive to external interference, the nucleus is reliably shielded from any outside influences. This makes it a potentially ideal "pendulum" for ultra-precise clocks.

The main obstacle was that the vast majority of nuclear transitions require colossal amounts of energy, beyond the reach of modern lasers. A fortunate exception turned out to be the isotope thorium-229. Back in 2003, physicists hypothesized that its unique properties would make it possible to create the first nuclear clocks.

In 2024, researchers managed to induce the necessary transition in the thorium-229 nucleus and record its "ticking." Now two independent groups of scientists have taken the crucial next step — turning this effect into a fully functional timekeeping device.

Both teams used calcium fluoride crystals embedded with thorium-229 nuclei. Vacuum ultraviolet laser radiation was used to control them.

For now, the new devices do not yet surpass the best atomic clocks in accuracy. However, scientists emphasize an important detail: atomic clocks have been refined for about 70 years, whereas nuclear clocks have only just been born. The researchers are convinced that the technology has proven its viability and is capable of rapid progress in the coming years.

The authors of the development are confident that in the future, such devices will find applications not only in ultra-precise timekeeping systems but also in fundamental physics — in particular, in the search for dark matter and in testing whether the fundamental constants of nature remain unchanged over time.