In his PhD thesis, Alexey Grinin performs the most accurate test of electrodynamics up do date

After six years at the Max Planck Institute of Quantum Optics (MPQ), Alexey Grinin successfully defended his PhD thesis on 18 August 2020; his doctoral thesis might help find the solution of one of the most prominent problems in physics.

January 27, 2021

The goal of his research project was to measure the absolute frequency of the 1S-3S-two-photon-transition in hydrogen and deuterium by using frequency comb spectroscopy. The result facilitated the most accurate test in quantum electrodynamics up to date. Grinin’s thesis, together with the result of the 1S-2S transition previously established by the research group of professor Hänsch, made it furthermore possible to improve the accuracy of the Rydberg constants by the factor 2, as well as establish an independent value for the proton charge radius. The result is especially interesting in the light of the so-called proton radius puzzle that describes the discrepancy between the proton charge radius from the spectroscopy of muonic and regular hydrogen. With his experimental thesis, Alexey Grinin was able to confirm the smaller proton charge radius, and move science closer to the solution of the proton radius puzzle. With the new two-photon-frequency-comb-spectroscopy, Alexey furthermore contributed to the advancement of precision spectroscopy in the ultraviolet region of the light spectrum.

What’s next?

For now, Alexey Grinin is planning to continue with the hydrogen project as a Postdoc at MPQ so he can test the limits of the experiment yet undiscovered. This could enlarge the scientific community’s understanding of quantum electrodynamics and the possibilities of precision spectroscopy in the future.

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