Advancing optical lattice clock performance with novel clock-line laser cooling techniques

Optical lattice clocks have demonstrated unprecedented performance below the 10^-18 fractional level, advancing towards new standards of timekeeping and sensitive probes in fundamental physics. To further advance optical lattice clocks performance, it is crucial to attain lower temperatures which facilitates the use of shallow lattices with reduced light shifts, while retaining large atom numbers to reduce the quantum projection noise. Here, we present Sisyphus cooling using the long-lived 3P0 clock state in alkaline-earth-like ytterbium. Upon excitation on the ultranarrow clock transition, Sisyphus cooling is observed within a spatially periodic potential induced by a 1388-nm optical standing wave that is nearly resonant with the 3P0 → 3D1 transition. Our cooling demonstrates versatility, working both in free space and in a magic-wavelength lattice. It offers the flexibility of being employed in either pulsed or continuous modes, making it suitable to a range of quantum metrology applications.