Lutetium clock loses 1 second every 264 billion years

TechRadar reports that researchers at the National University of Singapore (NUS) have set a new atomic-clock accuracy record with two clocks based on a single lutetium ion. A paper in Nature reports evaluated fractional uncertainties of 1.2 × 10⁻¹⁹ and 1.3 × 10⁻¹⁹, the lowest yet reported for an atomic clock. The 1.2 × 10⁻¹⁹ result corresponds to an error of about 1 second every 264 billion years.

The result is about 3.7 times lower than the previous record: a calcium-ion clock from the Chinese Academy of Sciences in Wuhan, which reported 4.4 × 10⁻¹⁹ in February 2026. It is 4.6 times lower than the aluminum-ion clock unveiled by NIST in July 2025, which reported 5.5 × 10⁻¹⁹.

NUS’s Centre for Quantum Technologies (CQT) compared its independent clocks for 200 hours using correlation spectroscopy. The clocks agreed within 5.7 × 10⁻¹⁹, which the team describes as the most precise clock comparison yet. Unlike the Wuhan clock, which used liquid nitrogen to cool its ions’ surroundings to about 80 kelvin, the lutetium clocks ran at room temperature in linear Paul traps without magnetic shielding.

The result could inform debate over replacing the cesium-based definition of the second, in use since 1967. Optical clocks can outperform cesium by up to 100 times, but a successor has not been selected. A draft resolution for the General Conference on Weights and Measures meeting in Versailles on October 13–15, 2026, asks for a proposal at its 2030 meeting. The team’s next step, joint first author Michael Lee says, is to miniaturize a lab-scale clock into a transportable system.