In 2021, we began designing and building the ROYMAGE (Mobile Ytterbium Optical Clock Applied to Geodesic Exploration) neutral ytterbium optical clock. After caesium, rubidium, strontium and mercury, we are now studying a fifth element at SYRTE, as a new definition of the second takes shape.

As predicted by Einstein as early as 1907, time is coupled to the gravitational potential: this is the so-called gravitational time dilation effect. For an atomic clock, this translates into a coupling between frequency and the geopotential experienced locally by the atoms.

We are therefore building the ROYMAGE instrument to be transportable. It will feature the ability to be connected to the ~60 outputs of the REFIMEVE fiber network (dissemination of an accurate ultrastable carrier at 1542 nm), and thus be compared to the ~12 European stationary optical clocks. These measurements will contribute to altitude references and geoid definition, particularly in areas where conventional geodesy methods (levelling, satellites) are sometimes ill-suited to sudden changes in gravitational potential.

More details on the website of ANR ROYMAGE.