Microscopy of quantum correlations in an ultracold molecular gas

Abstract

Ultracold molecules are a promising platform for quantum simulation of many-body physics due to their long-range dipolar interactions, rich set of internal states, and long coherence times. However, their complexity also makes it challenging to detect individual molecules and achieve control over their quantum states and interactions. In this thesis, I describe the development of a novel apparatus for performing quantum simulation experiments with ultracold NaRb molecules that addresses these challenges. We first form NaRb molecules in a well-defined quantum state in an optical lattice by associating atom pairs from ultracold gases of Na and Rb. Single molecules are then detected on individual sites via a high-resolution imaging system using a technique sensitive to their rotational state. We also describe the capabilities of the apparatus to control the dipolar interactions with AC and DC electric fields.Using this molecular quantum gas microscope apparatus, we measure the dynamics of site-resolved quantum correlations between the molecules due to their dipolar interactions. By using microwaves to address a two-level subspace of the rotational manifold of the molecules, we realize a spin-exchange model where the spins are coupled via the dipolar interactions. We prepare the synthetic spin system in an out-of-equilibrium state with a quench, and measure the evolution of spin correlations as the quantum system thermalizes. In addition, we demonstrate control over the dipolar interactions between the molecules by tuning their spatial anisotropy. Finally, we use Floquet driving to engineer a spin-anisotropic Heisenberg model from the native spin-exchange model. These experiments expand the capabilities of ultracold molecules for studying problems in quantum magnetism and quantum many-body physics more broadly. For example, future work could explore microscopic correlations in the dipolar Hubbard model, or characterize entangled states of interacting polar molecules relevant for quantum metrology.