Accuracy of quantum simulators with ultracold dipolar molecules: a quantitative comparison between continuum and lattice descriptions

TL;DR

This paper compares continuum and lattice models of ultracold dipolar bosons, revealing the limitations of single-band models in strong interaction regimes and highlighting the need for more complex descriptions.

Contribution

It provides a quantitative analysis of the validity of lattice models for dipolar gases, emphasizing the importance of multi-band effects in certain regimes.

Findings

Continuum and lattice models agree at weak interactions and low densities.

Strong DDI and high densities cause significant discrepancies between models.

Two-band Hubbard models improve the accuracy but still show deviations.

Abstract

With rapid progress in control and manipulation of ultracold magnetic atoms and dipolar molecules, the quantum simulation of lattice models with strongly interacting dipole-dipole interactions (DDI) and high densities is now within experimental reach. This rapid development raises the issue about the validity of quantum simulation in such regimes. In this study, we address this question by performing a full quantitative comparison between the continuum description of a one-dimensional gas of dipolar bosons in an optical lattice, and the single-band Bose-Hubbard lattice model that it quantum simulates. By comparing energies and density distributions, and by calculating direct overlaps between the continuum and lattice many-body wavefunctions, we demonstrate that in regimes of strong DDI and high densities the continuum system fails to recreate the desired lattice model. Two-band Hubbard models become necessary to reduce the discrepancy observed between continuum and lattice descriptions, but appreciable deviations in the density profile still remain. Our study elucidates the role of strong DDI in generating physics beyond lowest-band descriptions and should offer a guideline for the calibration of near-term dipolar quantum simulators.