Speaker
Description
Quantum electrodynamics (QED) forms the basis for all other quantum field theories, upon which the Standard Model (SM) of particle physics is constructed. Because of the hydrogen atom's simplicity, its energy levels can be precisely calculated from bound-state QED and compared with experiment. Such a comparison between theory and experiment is linked to the determination of fundamental constants that enter the theory as parameters. Only if there are more independent measurements than parameters can the theory be tested. For hydrogen, the theory test concerns the Rydberg constant and the proton radius. This requires at least two different transition-frequency measurements to determine them, and more measurements to test the theory. Here, we report on our recently published 2S-6P transition frequency measurement [1], which can be combined with the 1S-2S measurement [2] and the muonic proton radius [3,4]. We thereby test the SM prediction to 0.7 parts per trillion, which is comparable to the SM test with the anomalous magnetic moment (g-2) [5]. The bound-state QED corrections are tested to 0.5 parts per million, the most precise test to date.
[1] L. Maisenbacher, V. Wirthl et al., Nature 650 (2026)
[2] C. G. Parthey et al., PRL 107 (2011)
[3] R. Pohl et al., Nature 466 (2010)
[4] A. Antognini et al., Science 339 (2013)
[5] X. Fan et al., PRL 130 (2023)