Absolute frequency of 87Sr at 1.8 × 10−16 uncertainty by reference to remote primary frequency standards. (15th February 2021)

• Record Type: Journal Article
• Authors: Nemitz, Nils; Gotoh, Tadahiro; Nakagawa, Fumimaru; Ito, Hiroyuki; Hanado, Yuko; Ido, Tetsuya; Hachisu, Hidekazu
• Is Part Of: Metrologia. Volume 58:Number 2(2021)
• Publication Date: 2021-02-15
• Subjects: atomic clock -- frequency standard -- SI second -- strontium -- optical clock -- lattice clock; Weights and measures -- Periodicals; Weights and Measures -- Periodicals; 530.805
• DOI: 10.1088/1681-7575/abc232
• Languages: English
• ISSNs: 0026-1394

Abstract

Abstract: The optical lattice clock NICT-Sr1 regularly reports calibration measurements of the international timescale TAI. By comparing measurement results to the reports of eight primary frequency standards, we find the absolute frequency of the 87 Sr clock transition to be f S r = 429 228 004 229 873.082 76 H z, with a fractional uncertainty of less than 1.8 × 10 −16 approaching the systematic limits of the best realization of the SI second. Our result is consistent with other recent measurements and further supported by the loop closure over the absolute frequencies of 87 Sr, 171 Yb and direct optical measurements of their ratio.