Exploring spin physics with ultracold atoms

Abstract

The dynamics of many interacting spins is an active frontier of research; not only can they explain magnetic phenomena, but they also provide paradigmatic models with deep connections to high-T_c superconductivity, optimization problems, neural networks, and more. Experiments with ultracold alkali atoms in optical lattices have realized spin models with great success. In particular, the isotropic Heisenberg model---the XXX model---was realized more than a decade ago. The ⁷Li apparatus described here was the first to realize a tunable, anisotropic Heisenberg model, also known as the XXZ model.

In this thesis, I will describe how the capabilities of this apparatus were harnessed to characterize the spin models we realize, employ them to observe new resonances, and to contribute to studies in spin squeezing and fundamental physics. First, I will discuss how we prepared and observed phantom helix states: eigenstates of the XXZ Hamiltonian. Our understanding of the contact interactions and the phantom helix states enabled us to observe long-predicted lattice-induced resonances, whose effects can be leveraged as another knob to tune the XXZ Hamiltonian. Furthermore, our control over the spin system allowed us to generate spin-squeezed states, a paradigmatic form of entanglement for spin ensembles. This is the first time squeezed states were realized with nearest-neighbor contact interactions in a lattice. Finally, our control over the spin degree of freedom and defects in our state preparation allowed us to create pristine periodic lattices with which to study gedankenexperiments in light scattering.