Exploring Atom-Light Scattering in the Quantum Regime

Abstract

Ultracold atoms and molecules are promising platforms for exploring modern quantum science and technologies, such as quantum simulation and quantum computation. Here, light is the essential tool to manipulate and probe these systems. However, unlike in condensed matter systems where scattering experiments are routinely employed to characterize materials, ultracold atom and molecule systems are usually probed by imaging and not by light scattering.

In this thesis, I present a systematic investigation of atom-light scattering under various scenarios. When atoms are confined in optical lattices, light scattering can be used to explore single-body, two-body, and many-body physics. Focusing on single-atom physics, I study coherent and incoherent light scattering of single-atom wavepackets and the relation to which-way information. For two atoms tightly localized to a 20nm size on the same lattice site, I demonstrate the strong electric dipolar interactions between them, which result in large momentum transfers and spectroscopic shift of the resonance. On the many-body side, I show how light scattering can reveal distinct quantum phases at thermal equilibrium or defect generation in dynamical ramps. For atoms released from the optical lattice, I demonstrate that light scattering can read out the quantum statistical information and initial density correlations hidden in the interference of atomic wavepackets.

When atoms move freely in the form of degenerate quantum gases, I investigate how quantum statistics, phase transition, and interactions modify the atomic pair correlation and consequently the light scattering. For thermal gas at high density, I demonstrate nonlinear optical effects from high optical density and high scattering rate.

Finally, I describe our recent efforts on manipulating atoms at subwavelength length scales. I discuss our attempts in optical tweezers and in optical lattices, and the prospect of observing magnetic pairing between two distant layers under attractive dipolar interaction.

The techniques presented in this thesis should be of general use for pursuing quantum science and technology with ultracold atoms and molecules.