Testing atomic QED theory using a metastable helium Bose-Einstein condensate

Time: 1pm AEST - Melbourne, Sydney, Canberra, Brisbane; 3pm NZST.

Speaker: Dr Sean Hodgman
Affiliation: Australian National University

Abstract

Ultracold helium atoms trapped in the first excited state (termed metastable helium) form an ideal testbed for some of the most fundamental theories of quantum physics.  I will report on our recent work at ANU testing a fundamental cornerstone of quantum physics, atomic quantum electro dynamics (QED) theory. This theory describes the energy level structure of atoms at an extremely precise level that modern experiments are now able to challenge. Such precise experiments can require revisions and extensions to QED theory to be considered, such as the recent proton radius puzzle. The simple atomic structure of helium makes it an ideal test bed for QED theory, and I will report on a number of atomic energy level measurements we have performed recently. The most important of these involves a measurement of a tuneout wavelength, where the dipole shift from all different energy levels cancels out. This makes a tuneout measurement a highly precise probe of QED, as it simultaneously tests contributions from all atomic energy levels. Our result challenges the current level of QED theory.