# Fluorescence detection of single lithium atoms in an optical lattice using Doppler-cooling beams

## TL;DR

This paper demonstrates in situ fluorescence detection of single lithium atoms in a 1D optical lattice with high precision, using molasses beams for cooling and fluorescence collection, and models atom lifetime dependence on well depth.

## Contribution

It introduces a simple model for atom lifetime in optical lattices and achieves single-atom detection with high accuracy despite low photon collection efficiency.

## Key findings

- Atoms remain trapped for 30 s at 2.4 mK well depth.
- Single atom detection achieved within 300 ms with less than 0.0005 error.
- Fluorescence detection is effective even with low photon collection efficiency.

## Abstract

We demonstrate in situ fluorescence detection of $^7$Li atoms in a 1D optical lattice with single atom precision. Even though illuminated lithium atoms tend to boil out, when the lattice is deep, molasses beams without extra cooling retain the atoms while producing sufficient fluorescent photons for detection. When the depth of the potential well at an antinode is 2.4 mK, an atom remains trapped for 30 s while scattering probe photons at the rate of $1.7 \times 10^5$ s$^{-1}$. We propose a simple model that describes the dependence of the lifetime of an atom on well depth. When the number of trapped atoms is reduced, a clear stepwise change is observed in integrated fluorescence, indicating the detection of a single atom. At a photon-collecting efficiency of only 1.3% owing to small numerical aperture, the presence or absence of an atom is determined within 300 ms with an error of less than $5 \times 10^{-4}$.