Tackling the Blackbody Shift in a Strontium Optical Lattice Clock

A major obstacle for optical clocks is the frequency shift due to blackbody radiation (BBR). We discuss how one can tackle this problem in an optical lattice clock, in our case, ⁸⁷Sr: first, by a measurement of the dc-Stark shift of the clock transition and, second, by interrogating the atoms in a cryogenic environment. Both approaches rely on transporting ultracold atoms over several centimeters within a probe cycle. We evaluate the mechanical movement of the optical lattice and conclude that it is feasible to transport the atoms over 50 mm within 300 ms. With this transport, a dc-Stark shift measurement will allow reducing the contribution of the BBR to fractional uncertainty below 2 × 10^-17 at room temperature by improving the shift coefficient, known only from atomic-structure calculations up to now. We propose a cryogenic environment at 77 K that will reduce this contribution to a few times 10^-18.