Challenging QED with Hydrogen

• Applicant: Artur Matveev, Ph.D.
• Subject Area: Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas
• Term: from 2017 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 390524307

The goal of the project is to improve current tests of quantum electrodynamics exploiting high-precision spectroscopy of atomic hydrogen or similar simple systems.Modern quantum electrodynamics (QED) allows to compute the energy of transitions in simple atomic systems with a very high accuracy. Comparison of QED predictions with results of high precision spectroscopy opens the possibility to make precise tests of QED and extract the values of fundamental constants, such as the Rydberg constant and the Proton charge radius. Further progress in this direction requires high precision measurements of energies of relatively wide transitions, with uncertainty on the level of 100 ppm of observed linewidth. This is a very hard problem that has essentially stopped progress in the field for almost 20 years. Besides improved experimental capabilities it requires extremely good modelling of the observable line shape. Over the last couple of years I have developed a code that includes all known line shape distorting effect using a time-dependent density matrix equations and combined it with a large scale Monte Carlo simulation to mode the actual experimental situation for the hydrogen 2S-4P transition. With this we could illuminate the so called Proton Size Puzzle. This work has just been submitted to Science. We are in the process on working on the very favorable review reports. The key objective for continuing the project is to extend the model to other line shapes that are currently accessible by experiments. The 2S-nP (n=6,8,9,10) in atomic hydrogen and deuterium are coming into reach but require an even more complex treatment because of the large number of decay channels. While the 2S-4P involved 2704 coupled partial differential equations, the 2S-6P already requires 22,500 of these equations that I am handling in an analytic fashion using symbolic computer algebra. Completing of these objectives makes it possible to analyze the data from these experiments in collaboration with the group at the Max-Planck-Institute of Quantum Optics, Garching. This work could be of help for similar experiments at the Laboratoire Kastler Brossel, Paris and York University, Toronto. For that I would like to expand on a universal code on an open-source platform with a usable font end that can be used for simulating other atomic or molecular systems, which have computable energy levels. As the number of precisely computable systems have increased to 3 and 4 body systems (molecules, anti-photonic Helium etc.) a larger community is in need of precise modelling of their experimental setting. My code could help serving this community of atomic, molecular and optical physics.

• DFG Programme: Research Grants
• Cooperation Partners: Professor Dr. Theodor W. Hänsch; Professor Dr. Randolf Pohl; Professor Dr. Thomas Udem