Yb optical lattice clock
Since 1967, the SI second is defined on microwave frequency standards. However, atomic transitions in the optical domain show better stability and accuracy; this is the reason why the international metrology community is considering the possibility of a future redefinition of the second in terms of an optical frequency. In an ytterbium optical clock, the frequency of an ultra-stable laser is locked to the forbidden 1S0–3P0 transition of ytterbium prepared in an ultra-cold atom sample.
Our Yb clock has been characterized for the first time in 2016, when it has been measured respect to the Caesium fountain IT-CsF2. The measurement result was f(171Yb) = 518 295 836 590 863.59(31) Hz whit a relative uncertainty of 6e-16 limited by the Caesium fountain. This measurement is consistent and contributed to the recommended value for 171Yb as a secondary representation of the second in the International System of Units.
We are currently improving our setup for a new characterization aiming a relative uncertainty of 1e-17. For example we recently achieved high-resolution spectroscopy Fourier limited at 3 Hz level.