The Sr optical clock is the most widespread optical frequency standard around the world, the most stable and the most accurate. Its clock frequency has shown a reproducibility of uncertainty at the level of 10−17. Frequency comparisons of Sr clocks have been already used to constrain gravitational theories and are foreseen to be used in relativistic geodesy.

INRiM has assembled its own Sr optical lattice clock, and it presents some original solutions to have both an ultra-stable and accurate apparatus. In particular, it employs a 2D-MOT loaded atomic beam which ensures suppression of BBR shift from the atomic oven and an optical shutter of the Sr beam to suppress background collision shifts. Furthermore, it will guest a cavity-enhanced probing scheme to surpass the quantum projection noise limit and explore quantum-enhancement in optical clocks.