Laser cooling and qubit measurements on a forbidden transition in neutral Cs atoms

Abstract

We experimentally demonstrate background-free, hyperfine-level-selective measurements of individual Cs atoms by simultaneous cooling to $5.3\hat{I}¼\mathrm{K}$ and imaging on the $6s_{1/2}\to 5d_{5/2}$ electric-quadrupole transition. We achieve hyperfine resolved detection with fidelity 0.9993(4) and atom retention of 0.9954(5), limited primarily by vacuum lifetime. Performing state measurements in a 3D cooling configuration enables repeated low loss measurements. A theoretical analysis of an extension of the demonstrated approach based on quenching of the excited state with an auxiliary field, identifies parameters for hyperfine-resolved measurements with a projected fidelity of $\sim 0.9995$ in $\sim 60\hat{I}¼\mathrm{s}$.

Added coauthor C. Fang and information on bottle beam mask fabrication