Engineered Collisions, Molecular Qubits, and Laser Cooling of Asymmetric Top Molecules

Abstract

In this dissertation, I present studies of molecules for uses in quantum science ranging from quantum computing and ultracold collisions to controlling organic-inspired molecular species. Starting with a diatomic molecule, calcium monofluoride, we developed an optical tweezer platform for use in quantum computing and demonstrated rotational coherence times significantly longer than measured dipole-enabled gate times. Using the Tweezer platform, we studied ultracold collisions of exactly two molecules and exerted full quantum control over the internal structure of the molecules. The collisions resulted in a rapid loss from the tweezers, leading us to develop a microwave shield to prevent these lossy collisions. The shielding scheme enhanced the rate of elastic collisions enabling the demonstration of forced evaporative cooling.

To explore the possible use of larger molecules for quantum science, we studied the rotational structure of an asymmetric top and aromatic molecule, calcium monophenoxide, with the intent of identifying a path toward laser cooling and trapping. We cycled several photons, but theory predicted many more. After eliminating several decay paths, the key loss remained unknown. Applying the same methods to CaNH$_2$, a smaller asymmetric top molecule with similar spatial symmetry, we performed laser cooling. Using CaNH$_2$, we demonstrated photon cycling, and then observed Sisyphus cooling and heating features for the first time using an asymmetric top molecule. This work lays the foundation for future laser-cooling of organic-inspired molecules in an optical tweezer array for applications ranging from quantum computing to quantum chemistry, and precision measurement.