Interferometric thermometry of a single sub-Doppler cooled atom

TL;DR

This paper demonstrates a method for interferometric thermometry of a single sub-Doppler cooled atom by analyzing the self-interference contrast of emitted photons, showing potential for precise temperature measurements near the motional ground state.

Contribution

It introduces a novel setup combining sideband cooling and interference contrast measurement for single-atom thermometry near the motional ground state.

Findings

Achieved up to 90% interference contrast with the ion's mirror-image.

Demonstrated the dependence of interference contrast on the mean phonon number.

Showed potential for high-precision thermometry of single atoms.

Abstract

Efficient self-interference of single-photons emitted by a sideband-cooled Barium ion is demonstrated. First, the technical tools for performing efficient coupling to the quadrupolar transition of a single $^{138}$Ba$^{+}$ ion are presented. We show efficient Rabi oscillations of the internal state of the ion using a highly stabilized 1.76 $\mu m$ fiber laser resonant with the S$_{1/2}$-D$_{5/2}$ transition. We then show sideband cooling of the ion's motional modes and use it as a means to enhance the interference contrast of the ion with its mirror-image to up to 90%. Last, we measure the dependence of the self-interference contrast on the mean phonon number, thereby demonstrating the potential of the set-up for single-atom thermometry close to the motional ground state.