シンガポールの科学者らが、世界最高精度の原子時計を開発（Singapore scientists build world’s most accurate atomic clock）

2026-09-23 シンガポール国立大学（NUS）

＜関連情報＞

• https://news.nus.edu.sg/worlds-most-accurate-atomic-clock/
• https://www.nature.com/articles/s41586-026-11072-8

Lu +光周波数基準、精度は19桁目で検証済み Lu+ optical frequency references with accuracy verified at the 19th digit

K. J. Arnold, M. D. K. Lee, Qi Zhao, Qichen Qin, Zhao Zhang, N. Jayjong & M. D. Barrett
Nature  Published:23 September 2026
DOI:https://doi.org/10.1038/s41586-026-11072-8

Abstract

Optical atomic frequency references¹ have far surpassed their microwave frequency predecessors, leading to an anticipated redefinition of the SI (International System of Units) second². However, as the scientific community seeks consensus on a new standard, and several state-of-the-art optical standards now report evaluated fractional uncertainties below 10⁻¹⁸, verification by same-species comparisons to comparable levels remains an outstanding challenge. Here we report two ¹⁷⁶Lu⁺ single-ion optical frequency references, each with evaluated fractional frequency uncertainty near 1 × 10⁻¹⁹, which are directly compared by correlation spectroscopy and demonstrate agreement, with a measured relative frequency difference of [−0.1 ± (5.7)_stat ± (1.0)_sys] × 10⁻¹⁹, where ‘stat’ and ‘sys’ indicate the statistical and systematic uncertainty, respectively. Our optical references have been comprehensively assessed with evaluated uncertainties below 10⁻¹⁸, supported by a same-species comparison of independent systems to the 5.7 × 10⁻¹⁹ level. This accuracy, achieved in practical room-temperature systems, will contribute to improving international timekeeping and towards chronometric levelling^3,4 at the millimetre scale, as well as tests of fundamental physics⁵ such as Lorentz invariance⁶, general relativity⁷, searches for dark matter^8,9 and variation of fundamental constants^10,11.