BIPM, RIKEN, and Shimadzu Begin Collaboration to Explore the Role of Portable Optical Frequency Standards

Overview

The Bureau International des Poids et Mesures (BIPM), RIKEN, and Shimadzu Corporation have signed a memorandum of understanding to begin collaboration on the investigation and study of optical frequency standards (OFS). This memorandum establishes the initial framework for discussing and jointly examining the potential role of portable optical frequency standards in international time and frequency metrology.

Reliable comparisons between optical frequency standards are necessary to consider the future redefinition of the 'second'. One of the key requirements indicated by the Consultative Committee for Time and Frequency (CCTF) is that national metrology institutes can compare frequency standards under development with a relative uncertainty level of 10⁻¹⁸, and that optical frequency standards consistently contribute to Coordinated Universal Time (UTC). Portable optical frequency standards are being considered as one means to support such comparisons. Evaluating the practicality of portable devices and conducting technical studies on operational and environmental requirements is a crucial step in the broader roadmap towards the redefinition of the 'second' (Note).

In addition to BIPM, RIKEN, and Shimadzu Corporation, the National Metrology Institute of Japan (NMIJ) of the National Institute of Advanced Industrial Science and Technology is also expected to be involved in the discussions, and it is anticipated that an open system will be established where metrology institutes and related organizations from other countries can participate on equal terms.

The signing ceremony was held in Kawasaki City on May 12, 2026.

Note) N Dimarcq, et al. (2024) Roadmap towards the redefinition of the second. Metrologia doi: 10.1088/1681-7575/ad17d2

Background

Optical frequency standards, represented by optical lattice clocks and single-ion optical clocks, are based on optical transitions of atoms or ions and provide higher stability and accuracy than the microwave standards (e.g., cesium atomic clocks) that currently define the 'second'. Ensuring international consistency among these optical frequency standards is crucial for advancing the future redefinition of the 'second' in the International System of Units (SI).

Scene of the signing ceremony