Strontium lattice clocks for an optical second

Jérôme Lodewyck

Observatoire de Paris - SYRTE

Optical lattice clocks have now become the best frequency standards, by combining a high quality factor and a large number of interrogated ultra-cold atoms, tightly confined  in an optical lattice. Their fast progress makes a redefinition of the SI second using these clocks a possibility within the next decade. Optical lattice clocks have been developed at SYRTE with the objective to demonstrate that a complete architecture based on optical clocks can be realized : a set of two strontium optical lattice clocks, with a repeated agreement in the 10-17 range, have been characterized. These clocks are locally interconnected to high accuracy microwave primary and frequency standards, and a mercury optical lattice clocks. Phase compensated optical fiber links are now in operation to compare these clocks with optical clock in other European metrology institutes. Their operational development has led to improved tests of fundamental physics, such as the variability of fundamental constants or tests of Lorentz invariance. More recently, a first calibration of TAI with an optical transition have demonstrated the readiness of these clocks for the realization of an optical second.