Fig. 4: Bound-state QED tests in high electric fields.
The uncertainty of experiment and theory relative to the bound-state QED contribution for certain highlighted measurements are shown7,13,20,21,23,26,27,52,53. The separate measurements are summarized in Extended Data Table 4. The muonic and pionic points are Lamb-shift measurements of the bound-muon/bound-pion energy levels in an excited transition. Values above the diagonal line would benefit from an improved theoretical calculation. In those below the line, the experimental error is the dominating uncertainty. The added limit with improved experiment and theory assumes a mass measurement that improves the g factor to the Γ0 uncertainty, as well as an improvement of the theoretical value to the limit imposed by the finite nuclear size uncertainty.
