Keeping Time with Atoms on the Move

Optical lattice clocks use the natural rhythm of ultracold atoms as an extraordinarily precise tick. Most current designs operate in repeating cycles: the atoms are prepared, probed with the clock laser, and read out. Only the probing step compares the atoms with the laser, so the laser is not monitored during atom preparation and readout.

Researchers at the University of Tokyo, RIKEN, and JEOL Ltd. have demonstrated a new architecture for optical clocks, replacing a sequence in time with a division of labor in space. Atoms cooled in a magneto-optical trap are loaded into a moving optical lattice—an “optical conveyor belt” that carries them through separate zones for atom preparation, clock-laser probing, and readout. Because each operation has its own place, all three can proceed simultaneously as the atoms continue to flow. The experiment produced a sharply resolved clock spectrum from atoms in motion, showing that this architecture can support precision clock operation.

This result lays the foundation for optical lattice clocks that could monitor the clock laser continuously and reach stable readings more quickly. In the longer term, making these clocks compact and deployable would enable their use as field sensors. Comparing clocks at different locations would reveal small differences in gravitational potential, enabling measurements of elevation and deformation of the Earth’s crust.

Figure 1 | Clock operations arranged in space. Atoms cooled in a magneto-optical trap are loaded into a moving optical lattice, which carries them through three zones: atom preparation, clock-laser probing, and readout. Giving each operation its own location allows all three to proceed simultaneously as the atoms continue to flow.

Papers 
Journal: Nature Communications
Title: Spatially defined Rabi spectroscopy for uninterrupted optical clock interrogation
Authors: Koki Nishida, Ryoto Takeuchi, Shigenori Tsuji, Shoichi Okaba and Hidetoshi Katori
DOI: 10.1038/s41467-026-76017-1