Thorium Nuclear Clocks: A New Frontier of Precision express

Original: "Prospects for a Solid-State Nuclear Clock"

arXiv:2511.13017 · 2025-11-17 · CC BY 4.0 · 1 min

Atomic Physics Materials Other Condensed Matter Nuclear Experiment Nuclear Theory

Clocks based on the thorium-229 nucleus could become the most precise time-measuring instruments, surpassing all existing atomic clocks.

Ordinary atomic clocks rely on spectroscopy — counting electron oscillations. Thorium-229 nuclear clocks address the nucleus itself. Its excited state lives for 641 seconds: for nuclear physics, this is a pendulum in thick syrup, where one swing lasts an eternity, but is impeccably stable.

Placing such nuclei in a crystal, physicists face a problem: lattice defects act like an uneven floor, disrupting the rhythm of each pendulum in its own way. The task is to level this floor. Then the clocks will become more accurate: an error of one second over the entire age of the Universe. They will notice the difference in the passage of time between floors and test the Standard Model of physics for strength.

The concept was discussed as early as the mid-20th century, following the work of Isidor Isaac Rabi.

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Thorium-229 is the only nucleus whose transition can be triggered by a regular ultraviolet laser, rather than hazardous gamma radiation. This makes the experiments tabletop and safe.

Scientists

Christian Doppler D. B. McLaughlin Didier Queloz Michel Mayor R. A. Rossiter James Clerk Maxwell

Concepts

nuclear optical clock thorium 229 atomic clock half life crystal second tantalum nuclear stability solid state battery cesium chromium thorium lead nucleus lifetime time crystal solid state qubit proton spectroscopy

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Thorium Nuclear Clocks: A New Frontier of Precision express