⚛️ Scientists Have Built the World’s First Nuclear Clocks. They Could Change How We Measure Time.

For decades, the world’s most precise clocks have measured time using electrons moving between quantum energy levels inside atoms.

Now, two independent teams in Vienna and Beijing have demonstrated something physicists have pursued for more than 20 years:

Clocks that measure time using the atomic nucleus itself.

And the difference could be revolutionary.

Atomic nuclei are more than 10,000 times smaller than atoms and are generally much less sensitive to external electromagnetic disturbances.

That makes nuclear transitions exceptionally promising as stable frequency references.

The challenge? Almost every nuclear transition requires enormous energies, far beyond what conventional lasers can provide.

But one isotope is special: thorium-229.

Its nucleus has an unusually low-energy excited state that can be accessed using ultraviolet laser light at approximately 148 nanometers.

Researchers embedded thorium-229 nuclei inside tiny calcium fluoride crystals and developed lasers capable of detecting their nuclear transitions.

Then came the breakthrough.

They used the nuclear transitions themselves to automatically stabilize the laser frequency.

The result: two independently demonstrated, functioning nuclear clocks.

The European system operated continuously for approximately 24 hours, achieving fractional frequency instability approaching 10⁻¹⁵ after a day of averaging.

That’s an extraordinarily small fluctuation — although today’s best optical atomic clocks are still substantially more stable.

But the most exciting application might have nothing to do with telling time.

One team has already used its nuclear clock to search for dark matter.

Some theories predict that ultralight dark matter could cause tiny oscillations in fundamental physical constants, subtly changing how atomic nuclei behave.

By comparing nuclear and atomic clocks, physicists can search for these otherwise invisible effects.

The experiment found no dark matter signal, but it established new constraints on certain theoretical models.

And this is only the beginning.

Future nuclear clocks could potentially improve satellite navigation, measure gravitational effects with extraordinary precision and test whether the fundamental constants of physics really remain constant.

For thousands of years, humanity has built better clocks to understand time.

Now we’re building clocks that might help us understand the universe itself.

#Physics #QuantumPhysics #NuclearPhysics #AtomicClocks #DarkMatter #QuantumTechnology #Science

https://www.nature.com/articles/s41586-026-11084-4