Preparation of one 87Rb and one 133Cs atom in a single optical tweezer

Abstract

We report the preparation of exactly one ^87 Rb atom and one ^133 Cs atom in the same optical tweezer as the essential first step towards the construction of a tweezer array of individually trapped ^87 Rb ^133 Cs molecules. Through careful selection of the tweezer wavelengths, we show how to engineer species-selective trapping potentials suitable for high-fidelity preparation of Rb + Cs atom pairs. Using a wavelength of 814 nm to trap Rb and 938 nm to trap Cs, we achieve loading probabilities of 0.508(6) for Rb and 0.547(6) for Cs using standard red-detuned molasses cooling. Loading the traps sequentially yields exactly one Rb and one Cs atom in 28.4(6)% of experimental runs. Using a combination of an acousto-optic deflector and a piezo-controlled mirror to control the relative position of the tweezers, we merge the two tweezers, retaining the atom pair with a probability of $0.9{9}_{\left(-0.02\right)}^{\left(+0.01\right)}$ . We use this capability to study hyperfine-state-dependent collisions of Rb and Cs in the combined tweezer and compare the measured two-body loss rates with coupled-channel quantum scattering calculations.

Keywords

• optical tweezers
• species-selective
• merging
• collisions
• ultracold molecules