Isolating and manipulating single atoms

Abstract

In this thesis we study: the dynamics leading to a near-deterministic preparation of single atoms in a microscopic optical dipole trap; the non destructive imaging and counting of trapped atoms; and a system for sorting single atoms between optical dipole traps using a high numerical aperture lens and a spatial light modulator.

We near-deterministically prepare trapped single Rubidium atoms by exposing them to a tailored light field which induces light assisted collisions. By preparing pairs of Rubidium atoms in an optical micro-trap we can study the outcome of light assisted collisions at the single event level. Using this knowledge we tailor the light such that each collision releases only enough energy for one atom of a colliding atom-pair to escape the trap. This thereby yields an 83% single atom loading efficiency.

We demonstrate a method to count small numbers of atoms held in a deep, microscopic optical dipole trap by collecting fluorescence from atoms exposed to a standing wave of light that is blue-detuned from resonance. While scattering photons, the atoms are cooled by a Sisyphus mechanism that results from the spatial variation in light intensity. The use of a small blue detuning limits the losses due to light assisted collisions, thereby making the method suitable for counting several atoms in a microscopic volume.

We create two overlapping one-dimensional optical lattices using a single laser beam, a spatial light modulator and a high numerical aperture lens. These lattices have the potential to trap single atoms, and using the dynamic capabilities of the spatial light modulator may shift and sort atoms to a minimum atom-atom separation of 1.52 µm. We show how a simple feedback circuit can compensate for the spatial light modulator's intensity modulation.