Jul 17 – 22, 2022
Royal Conservatory of Music, Toronto
America/Toronto timezone

Experiment and theory for a helium tune-out frequency: an independent test of quantum electrodynamics

Jul 18, 2022, 5:00 PM
1h 30m
Hart House (Hart House)

Hart House

Hart House

7 Hart House Cir, Toronto, ON M5S 3H3
Poster presentation Precision measurement and tests of fundamental physics Poster session


Quantum electrodynamics (QED) is one of the most stringently tested theories underpinning modern physics. Nevdertheless, recent precision atomic spectroscopy measurements have uncovered several small discrepancies between experiment and theory. One particularly powerful experimental observable that tests QED independently of traditional energy level measurements is the tune-out frequency, where the dynamic polarizability vanishes and the atom does not interact with applied laser light. In our work, we measure the tune-out frequency for the $2\;^3S_1$ state of helium between transitions to the $2\;^3P_J$ and $3\;^3P_J$ manifolds and compare it with new theoretical QED calculations [1]. The experimentally determined value of 725,736,700(260) MHz differs from theory [725,736,252(9) MHz] by 1.7 times the measurement uncertainty and resolves both the QED contributions and retardation corrections. The underlying theory is formulated more generally as a zero in the forward Rayleigh scattering cross section, rather than a zero in the dynamic polarizability. Relativistic, QED, and retardation corrections are included in a nonrelativistic QED (nr-QED) approach

[1] B. M. Henson et al., Science 376, 199 (2022).

Presenter name Gordon Drake
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Primary authors

Gordon Drake (University of Windsor) Dr Bryce Henson (Austtralian National University) Dr Jacob Ross (Australian National University) Dr Kieran Thomas (Australian National University) Dr David Shin (Australian National University) Dr Sean Hodgman (Australian National University) Dr Yong-Hui Zhang (Wuhan Institute pf Physics and Mathematics) Dr Li-Yan Tang (Wuhan Institute of Physics and Mathematics) Mr Aaron Bondy (Univeristy of Windsor) Dr Andrew Truscott (Australian National University) Dr Carlos Kuhn (Australian National University) Dr Kenneth Baldwin (Australian National University)

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