Construction of a quantum gas microscope for fermionic atoms

Abstract

This thesis reports the construction of a novel apparatus for experiments with ultracold atoms in optical lattices: the Fermi gas microscope. Improving upon similar designs for bosonic atoms, our Fermi gas microscope has the novel feature of being able to achieve single-site resolved imaging of fermionic atoms in an optical lattice; specifically, we use fermionic potassium-40, sympathetically cooled by bosonic sodium-23. In this thesis, several milestones on the way to achieving single-site resolution are described and documented. First, we have tested and mounted in place the imaging optics necessary for achieving single-site resolution. We set up separate 3D magnetooptical traps for capturing and cooling both ²³Na and ⁴⁰K. These species are then trapped simultaneously in a plugged quadrupole magnetic trap and evaporated to degeneracy; we obtain a sodium Bose-Einstein condensate with about a million atoms and a degenerate potassium cloud cooled to colder than 1 [mu]K. Using magnetic transport over a distance of 1 cm, we move the cold cloud of atoms into place under the high-resolution imaging system and capture it in a hybrid magnetic and optical-dipole trap. Further evaporation in this hybrid trap performed by lowering the optical trap depth, and the cooled atoms are immersed in an optical lattice, the setup and calibration of which is also described here. Finally, we cool the atoms with optical molasses beams while in the lattice, with the imaging optics collecting the fluoresence light for high-resolution imaging. With molasses cooling set up, single-site fluoresence imaging of bosons and fermions in the same experimental apparatus is within reach.