Testing Quantum Electrodynamics with Exotic Atoms

Precision study of few-electron, high-$Z$ ions is a privileged field for probing high-field, bound-state quantum electrodynamics (BSQED). However, the accuracy of such tests is plagued by nuclear uncertainties, which are often larger than the BSQED effects under investigation. We propose an alternative method with exotic atoms and show that transitions may be found between circular Rydberg states where nuclear contributions are vanishing while BSQED effects remain large. When probed with newly available quantum sensing detectors, these systems offer gains in sensitivity of 1 to 2 orders of magnitude, while the mean electric field largely exceeds the Schwinger limit.

Figure 1

Size of the QED contributions to the $\mathrm{Ly}\alpha$ transition energy, scaled by $Z^4$ as a function of $Z$, and comparison to experimental uncertainty and uncertainty on the theoretical energy due to uncertainties in the nuclear size [41]. References for experiments: [6, 12, 14, 15, 16, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69]. Theory from [70]. Details and more comparisons can be found in [4].

Figure 2

(a) QED contribution to the transition energy as a function of the FNS contribution to the transition energy for yrast transitions in antiprotonic and muonic ${}^{132}\mathrm{Xe}$. (b) QED contribution to the transition energy as a function of the transition energy for yrast transitions in antiprotonic and muonic noble gases. In both (a) and (b), the $2p–1s$ transitions in H-like ions ($Z=18$, 26, 36, 54, 92) are shown for reference.