Impurity transport through a strongly interacting bosonic quantum gas

TL;DR

This study uses numerical simulations to explore how an impurity moves through a one-dimensional Bose gas, revealing how impurity behavior reflects the gas's interaction regime and excitation spectrum, with implications for non-destructive measurements.

Contribution

It demonstrates that impurity dynamics can non-invasively probe the Bose gas's properties and phase transitions, providing new insights into impurity transport in strongly interacting quantum systems.

Findings

Impurity behavior indicates the Bose gas's filling and excitation spectrum.

Impurity acts as a witness to the superfluid to Mott insulator transition.

Spatial coherence of the impurity correlates with its transport properties.

Abstract

Using near-exact numerical simulations we study the propagation of an impurity through a one-dimensional Bose lattice gas for varying bosonic interaction strengths and filling factors at zero temperature. The impurity is coupled to the Bose gas and confined to a separate tilted lattice. The precise nature of the transport of the impurity is specific to the excitation spectrum of the Bose gas which allows one to measure properties of the Bose gas non-destructively, in principle, by observing the impurity; here we focus on the spatial and momentum distributions of the impurity as well as its reduced density matrix. For instance we show it is possible to determine whether the Bose gas is commensurately filled as well as the bandwidth and gap in its excitation spectrum. Moreover, we show that the impurity acts as a witness to the cross-over of its environment from the weakly to the strongly interacting regime, i.e., from a superfluid to a Mott insulator or Tonks-Girardeau lattice gas and the effects on the impurity in both of these strongly-interacting regimes are clearly distinguishable. Finally, we find that the spatial coherence of the impurity is related to its propagation through the Bose gas, giving an experimentally controllable example of noise-enhanced quantum transport.