Highly excited eigenstates of interacting quantum systems are generically “thermal,” in the sense that physical observables behave as they would in thermal equilibrium--all initial conditions give rise to locally thermal behavior at times past the intrinsic dynamical timescale. Systems in which thermalization is absent are of great fundamental interest because they violate equilibrium statistical mechanics, and of technological interest because some quantum information encoded in these states evades decoherence. For the purpose of tackling this line of inquiry, ultracold neutral atoms in dilute gas offers a suitable tabletop platform that is well isolated from the environment and readily scalable to the thermodynamic limit.
In this talk, I will describe our recent efforts of creating nonthermal states in a bosonic quantum gas of dysprosium, the most magnetic element, confined in quasi-1D waveguides. With repulsive long-range dipolar interactions that are two orders of magnitude stronger than alkali atoms, a highly excited super-Tonks-Girardeau gas is stabilized against collapse and thermalization. Stiffness and energy-per-particle measurements indicate that the system is dynamically stable regardless of short-range contact interaction strength. This metastability enables the cycling of contact interactions from weakly to strongly repulsive, then strongly attractive, and finally weakly attractive via two neighboring magnetically tuned collisional resonances. Iterating this quantum holonomy cycle allows an energy-space topological pumping method to create a hierarchy of increasingly excited prethermal states. In addition to being the first experimental realization of a dipolar Luttinger liquid, the result opens up an unexplored regime of quantum control and may have wide-ranging implications for understanding the onset of chaos in near-integrable systems.
Wil Kao is an Applied Physics Ph.D. candidate at Stanford University, where he works on quantum simulation using dipolar quantum gases under the supervision of Prof. Benjamin Lev. He holds a B.A.Sc. in Engineering Science from the University of Toronto.