Optical frequency standards are the most promising candidates for the redefinition of the Second in the International System of Units, as they enable to achieve lower uncertainties than primary microwave clocks (cesium fountains).

The clock developed at INRIM has an uncertainty of 2 10^-17  and we are currently working to reduce the most relevant systematic effects, such as those due to blackbody radiation. In parallel, a second improved system with a lower sensitivity to environmental effects is under design.

In 2016, INRIM Yb optical clock participated, together with a transportable clock developed at PTB, to a proof-of-principle geodesy experiment where such devices were used as probes of the gravitational potential.