We report an s-wave collisional frequency shift of an atomic clock based on fermions. In contrast to bosons, the fermion clock shift is insensitive to the population difference of the clock states, set by the first pulse area in Ramsey spectroscopy, θ1. The fermion shift instead depends strongly on the second pulse area θ2. It allows the shift to be canceled, nominally at θ2=π/2, but correlations perturb the null to slightly larger θ2. The frequency shift is relevant for optical lattice clocks and increases with the spatial inhomogeneity of the clock excitation field, naturally larger at optical frequencies.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy(all)