Prospects for measuring the electric dipole moment of the electron using electrically trapped polar molecules

TL;DR

This paper evaluates the potential of using electrically trapped polar molecules to measure the electron's electric dipole moment with higher precision than current beam experiments, focusing on coherence times and experimental challenges.

Contribution

It provides a detailed analysis of the sensitivity improvements and technical challenges in trapping molecules for EDM measurements, proposing a feasible experimental setup.

Findings

Trap-based measurements could be ten times more sensitive than beam experiments.

Loading from larger emittance sources could increase sensitivity by a factor of five.

Field inhomogeneity and geometric phase shifts are key obstacles to overcome.

Abstract

Heavy polar molecules can be used to measure the electric dipole moment of the electron, which is a sensitive probe of physics beyond the Standard Model. The value is determined by measuring the precession of the molecule's spin in a plane perpendicular to an applied electric field. The longer this precession evolves coherently, the higher the precision of the measurement. For molecules in a trap, this coherence time could be very long indeed. We evaluate the sensitivity of an experiment where neutral molecules are trapped electrically, and compare this to an equivalent measurement in a molecular beam. We consider the use of a Stark decelerator to load the trap from a supersonic source, and calculate the deceleration efficiency for YbF molecules in both strong-field seeking and weak-field seeking states. With a 1s holding time in the trap, the statistical sensitivity could be ten times higher than it is in the beam experiment, and this could improve by a further factor of five if the trap can be loaded from a source of larger emittance. We study some effects due to field inhomogeneity in the trap and find that rotation of the electric field direction, leading to an inhomogeneous geometric phase shift, is the primary obstacle to a sensitive trap-based measurement.