Towards an optical clock for space: Compact, high-performance optical lattice clock based on bosonic atoms

Optical clocks operated on satellites are expected to open up new opportunities in time transfer, geodesy,
fundamental physics, and satellite navigation. Here we demonstrate an important first step towards this goal:
a modular, compact, optical lattice clock (OLC) system that achieves 2.0 × 10−17 fractional uncertainty. The
clock is operated with bosonic strontium and improves the performance of bosonic OLCs by a factor of 30.
This has important implications for future use of bosonic OLCs in fundamental physics and metrology. We
make use of the clock’s metrological performance to measure, with independent clocks, the isotope shift of the
1S0 → 3P0 transitions of 88Sr and 87Sr, with an uncertainty of 12 mHz. The ratio of the transition frequencies is
thus determined with 3 × 10−17 fractional uncertainty.