近日，新加坡国立大学Barrett, M. D.团队报道了精度验证达第19位数字的Lu⁺光学频率参考。该研究于2026年9月23日发表在《自然》杂志上。

光学原子频率参考已远远超越其微波频率前身，从而预期将推动国际单位制（SI）秒的重新定义。然而，在科学界就新标准寻求共识、且若干最先进的光学标准目前报告评估的相对不确定度已低于10^-18之际，通过同种比较验证到相当水平仍是一项重大挑战。

研究组报道了两个¹⁷⁶Lu⁺单离子光学频率参考，二者评估的相对频率不确定度均接近1 × 10^-19；通过关联光谱对它们进行直接比较，结果显示二者一致，测得的相对频率差为[−0.1 ± (5.7)_stat ± (1.0)_sys] × 10^-19，其中“stat”和“sys”分别表示统计不确定度和系统不确定度。该光学参考已得到全面评估，评估不确定度低于10^-18，并得到独立系统同种比较达到5.7 × 10^-19水平的支持。这种在实用室温系统中实现的精度，将有助于改进国际计时，并推动毫米尺度的计时水准测量，以及基础物理检验，如洛伦兹不变性、广义相对论、暗物质搜寻和基本常数变化。

附：英文原文

Title: Lu+ optical frequency references with accuracy verified at the 19th digit

Author: Arnold, K. J., Lee, M. D. K., Zhao, Qi, Qin, Qichen, Zhang, Zhao, Jayjong, N., Barrett, M. D.

Issue&Volume: 2026-09-23

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 1018, 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 × 1019, 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] × 1019, where ‘stat’ and ‘sys’ indicate the statistical and systematic uncertainty, respectively. Our optical references have been comprehensively assessed with evaluated uncertainties below 1018, supported by a same-species comparison of independent systems to the 5.7 × 1019 level. This accuracy, achieved in practical room-temperature systems, will contribute to improving international timekeeping and towards chronometric levelling3,4 at the millimetre scale, as well as tests of fundamental physics5 such as Lorentz invariance6, general relativity7, searches for dark matter8,9 and variation of fundamental constants10,11.

DOI: 10.1038/s41586-026-11072-8

Source: https://www.nature.com/articles/s41586-026-11072-8