Preparation of mesoscopic atomic ensembles with single-particle resolution

TL;DR

This paper introduces a fluorescence detection method capable of resolving individual atoms in ensembles of up to approximately 390 atoms, enabling precise atom number control for quantum state applications.

Contribution

The authors developed an integrated fluorescence detection technique with single-atom resolution applicable to ensembles of up to 390 atoms, improving atom number measurement accuracy for quantum experiments.

Findings

Achieved single-atom resolution for 1 to 30 atoms.

Extrapolated resolution limit to about 390 atoms.

Demonstrated 92% fidelity in preparing 7-atom ensembles with reduced number fluctuations.

Abstract

The analysis of entangled atomic ensembles and their application for interferometry beyond the standard quantum limit requires an accurate determination of the number of atoms. We present an accurate fluorescence detection technique for atoms that is fully integrated into an experimental apparatus for the production of many-particle entangled quantum states. Single-particle resolving fluorescence measurements for $1$ up to $30$ atoms are presented. According to our noise analysis, we extrapolate that the single-atom resolution extends to a limiting atom number of $390(20)$ atoms. We utilize the accurate atom number detection for a number stabilization of the laser-cooled atomic ensemble. For a target ensemble size of $7$ atoms prepared on demand, we achieve a $92(2)\,\%$ preparation fidelity and reach number fluctuations $18(1)\,\mathrm{dB}$ below the shot noise level using real-time feedback on the magneto-optical trap.