Preparation and characterisation of an array of trapped single neutral Rb-87 atoms for quantum computation and quantum simulation

Abstract

This thesis investigates the experimental realization and characterization of single neutral 87'1 atoms trapped in optical tweezer arrays, a critical step toward developing scalable quantum processors with long coherence times. An Acousto-Optic Deflector (AOD) conjugated to a high-NA microscope objective generates multiple diffraction-limited spots from the 813 nm trapping laser. These tweezers are loaded from the centre of a Magneto-Optical Trap (MOT) cloud. A primary focus of this thesis is the light-assisted collisions mechanism, which is responsible in reducing the trap occupation numbers to sub-Poissonian values via pairwise/ singular trap losses. Hence, the cooling 780 nm laser is used for both fluorescence imaging as well as inducing these inelastic collisions. Theoretically, operating in the ”collisional blockade regime” should limit trap occupancy to a single atom by ensuring trap loss rates dominate loading rates. Experimental characterization of atom occupation trends involved both red- and blue-detuned collision beams. Results indicated a beam waist of 1.83 um which exceeds the sub-micron threshold required for a robust collisional blockade. Consequently, the fluorescence histograms revealed multi-modal signatures (0 to 3 atoms) rather than the ideal bimodal (0 or 1) occupancy. However, a significant reduction in mean occupation at higher detunings confirmed the effectiveness of the collision mechanism in achieving sub-Poissonian statistics. The work further details the design of a miniaturized, portable science chamber intended for field-deployed quantum computing. While the initial vacuum bake-out failed to reach Ultra-High Vacuum (UHV) due to epoxy cracking in the custom cell, the design remains a viable prototype for future iterations. Furthermore, the temporal responsivity of an AOM was investigated for possible generation of time-shared arrays of trapped single atoms. This work successfully demonstrates the generation of a 1D array of trapped atoms with multimodal occupations, and provides a comprehensive analysis of loading dynamics and hardware constraints. The findings emphasize that AOD operational wavelengths, objective numerical aperture, and imaging losses are critical factors in perfecting scalable neutral-atom qubit arrays.