# Thorium Nuclear Clock Breakthrough

> Scientists create first optical nuclear clock using thorium-229, achieving unprecedented stability for dark matter detection.
- Title: Thorium Nuclear Clock Breakthrough · Nature | Shortify
- Summary: Scientists create first optical nuclear clock using thorium-229, achieving unprecedented stability for dark matter detection. Researchers built a thorium-229…
- Keywords: thorium-229, nuclear clock, dark matter, optical clock, calcium fluoride, yba+, fractional frequency instability, science, Thorium, Nuclear, Clock, Breakthrough
- Source: Nature — https://nature.com/articles/s41586-026-11084-4
- Published: 2026-10-07T00:00:00+00:00
- Read time: 1 min
- Topics: thorium-229, nuclear clock, dark matter, optical clock, calcium fluoride, yba+, fractional frequency instability, science
## Thorium-229 Nuclear Clock Realized
Scientists created the first optical nuclear clock using thorium-229, stabilizing a laser to its 148-nm nuclear transition.
## Room-Temperature Crystal Setup
Thorium-229 nuclei are embedded in a millimetre-sized, room-temperature calcium fluoride crystal for stability.
## Subharmonic Laser Comparison
A subharmonic of the 148-nm radiation is continuously compared with a Yb+ single-ion clock for precision.
## Shot-Noise Limited Stability
The clock shows a shot-noise-limited fractional frequency instability of 3×10^-12/√(τ/s) over 1 day of operation.
## Dark Matter Detection
Researchers used the clock to search for periodic fluctuations in the nuclear transition energy between 20 seconds and 1 day.
## Enhanced Dark Matter Constraints
The clock's sensitivity improves dark matter coupling measurements beyond previous atomic clock results.
## Key takeaway

Researchers built a thorium-229 nuclear clock with 10^-15 stability over a day, using it to constrain ultralight dark matter models.