Abstract
We report the preparation of exactly one 87Rb atom and one 133Cs atom in the same optical tweezer as the essential first step towards the construction of a tweezer array of individually trapped 87Rb133Cs 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 . 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.
Highlights
Introduction ceOptical tweezers have emerged as a powerful experimental technique for quantum science owing to the inherent capability to prepare, address and detect single neutral atoms.Utilising optical tweezers, it is possible to produce large filled arrays of single atoms using dynamic rearrangement [1, 2, 3, 4, 5] and enhanced loading techniques [6, 7]
Our chosen wavelengths lie outside the enclosed triangular region for equal intensity tweezers shown in figures 1(d) and (e), experimentally we use twice as much power in the 938 nm tweezer as in the 814 nm tweezer. This increases the confinement of the Cs atom sufficiently that it is not expelled by the Rb tweezer during merging
Since we aim to trap only a few atoms in the optical tweezers, each magneto-optical trap (MOT) is typically loaded for just 150 ms to produce clouds of 1/e width ∼ 100 μm containing less than 106 atoms
Summary
The preparation of heteronuclear atom pairs in a single optical tweezer, and the subsequent separation of the atoms back into their original tweezers for detection, are best achieved using species-selective optical tweezers. We require that |ŨCs (λCs )| > |ŨCs (λRb )| in the range of valid λRb identified, so that the Cs ce pte an us cri atom is not expelled from its tweezer by repulsion from the Rb tweezer (as illustrated, inset) To understand how these two conditions can be satisfied, we consider the potential experienced by each atom in the overlapped tweezers, using figures 1(c-e). Our chosen wavelengths lie outside the enclosed triangular region for equal intensity tweezers shown in figures 1(d) and (e), experimentally we use twice as much power in the 938 nm tweezer as in the 814 nm tweezer This increases the confinement of the Cs atom sufficiently that it is not expelled by the Rb tweezer during merging
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