NUS Reports Lutetium-Ion Clocks With Record 1.2 × 10⁻¹⁹ Uncertainty
Two clocks ran for 200 hours and agreed to within 5.7 × 10⁻¹⁹, according to research by the National University of Singapore's Centre for Quantum Technologies.
A team at the National University of Singapore's Centre for Quantum Technologies has reported two lutetium-ion clocks with evaluated fractional uncertainties of 1.2 × 10⁻¹⁹ and 1.3 × 10⁻¹⁹, the lowest yet reported for any atomic clock, according to techradar.com.
The two clocks were compared over 200 hours using correlation spectroscopy and agreed to within 5.7 × 10⁻¹⁹. An uncertainty of 1.2 × 10⁻¹⁹ corresponds to one second of error in roughly 264 billion years.
The group has worked on lutetium for more than a decade. The team now plans to miniaturize the lab-scale clock into a transportable system.
Context for the record
The result comes as other ion-clock records have been reported. In February 2026, the Chinese Academy of Sciences in Wuhan reported a calcium-ion clock at 4.4 × 10⁻¹⁹, following NIST's aluminum-ion clock at 5.5 × 10⁻¹⁹ in July 2025. The definition of the second has rested on cesium since 1967, and the General Conference on Weights and Measures meets in Versailles from October 13 to 15, 2026.
Quick answers
What uncertainty did the NUS lutetium-ion clocks achieve?
The two clocks had evaluated fractional uncertainties of 1.2 × 10⁻¹⁹ and 1.3 × 10⁻¹⁹, and agreed to within 5.7 × 10⁻¹⁹ over 200 hours.
What does an uncertainty of 1.2 × 10⁻¹⁹ mean in practice?
It corresponds to one second of error in roughly 264 billion years.
What is next for the NUS clock project?
The team plans to miniaturize the lab-scale clock into a transportable system.