A Michelson-Morley test for electrons using trapped ions

Professor Hartnut Häffner (host Kislat), UC Berkely
November 10, 2017 at 2:00 pm
241 Compton
Event Description 

Lorentz symmetry is one of the corner stones of modern physics. As such it should not only hold for photons, but also for other particles such as the electron. Here we search for violation of Lorentz symmetry by performing an analogue of a Michelson-Morley experiment for electrons. We split an electron-wavepacket bound inside a calcium ion into two parts with different orientations. As the Earth rotates, the absolute spatial orientation of the wavepackets changes and anisotropies in the electron dispersion would modify the phase of the interference signal. To remove noise, we prepare a pair of ions in a decoherence-free subspace, thereby rejecting magnetic field fluctuations common to both ions. After a 23 hour measurement, we limit the energy variations to 11 mHz, verifying the isotropy of the electron's motion at the 1E-18 level. Alternatively, we can interpret our result as testing the rotational invariance of the Coulomb potential. Assuming Lorentz symmetry holds for electrons and that the photon dispersion relation governs the Coulomb force, we obtain a new limit on anisotropies in the speed of light. We will also discuss how using Ytterbium instead of Calcium ions promises tighter bounds for Lorentz symmetry breaking in the electromagnetic sector.

Coffee: 1:45 pm, 241 Compton