AMO In the literature: open

Blackbody radiation shift of lattice clocks at the 1e-19 level

In plain words

Heat radiation from the room shifts atomic clock frequencies, and for strontium this is one of the largest uncertainties. Controlling it ten times better requires both temperature control and better atomic theory.

Precise statement

Determine the room-temperature (300 K) blackbody shift of the Sr (or Yb) 1S0-3P0 lattice-clock transition, including the dynamic correction from the frequency dependence of the differential polarizability, with fractional uncertainty below $1e-19$, and the effective radiation temperature seen by the atoms to 10 mK.

What would settle it

Measurement of the differential dynamic polarizability at mid-infrared frequencies combined with in-vacuum thermometry, or cryogenic clock operation that verifies the shift scaling with $T^{4}$ and $T^{6}$.