Collective state measurement of mesoscopic ensembles with single-atom resolution

TL;DR

This paper demonstrates single-atom resolution measurements of mesoscopic atomic ensembles with over 100 atoms using cavity resonance shifts, advancing quantum measurement capabilities for larger systems.

Contribution

It extends cavity-based detection with single-atom resolution to larger ensembles and enables Heisenberg-limited interferometry.

Findings

Achieved single-atom resolution for ensembles with over 100 atoms

Extended detection range by more than an order of magnitude

Enabled capabilities for Heisenberg-limited interferometry

Abstract

For mesoscopic ensembles containing 100 or more atoms we measure the total atom number and the number of atoms in a specific hyperfine state with single-atom resolution. The measurement detects the atom-induced shift of the resonance frequency of an optical cavity containing the ensemble. This work extends the range of cavity-based detection with single-atom resolution by more than an order of magnitude in atom number, and provides the readout capability necessary for Heisenberg-limited interferometry with atomic ensembles.