Measuring ion oscillations at the quantum level with fluorescence light

TL;DR

This paper presents an optical method capable of detecting atomic ion oscillations with single-phonon sensitivity, enabling precise motion measurement at the quantum level through interference of scattered light.

Contribution

The authors introduce a novel interference-based optical technique for measuring atomic motion with quantum sensitivity, achieving single-phonon detection near the ground state.

Findings

Detected atomic oscillations with single-phonon sensitivity.

Reconstructed average phase space trajectories of atomic motion.

Achieved motion detection near the quantum ground state after EIT cooling.

Abstract

We demonstrate an optical method for detecting the mechanical oscillations of an atom with single-phonon sensitivity. The measurement signal results from the interference between the light scattered by a single trapped atomic ion and that of its mirror image. The motion of the atom modulates the interference path length and hence the photon detection rate. We detect the oscillations of the atom in the Doppler cooling limit and reconstruct average trajectories in phase space. We demonstrate single-phonon sensitivity near the ground state of motion after EIT cooling. These results could be applied for motion detection of other light scatterers of fundamental interest, such as trapped nanoparticles.