A neutral-atom Hubbard quantum simulator in the cryogenic regime

TL;DR

This paper demonstrates a significant temperature reduction in ultracold fermionic atoms in optical lattices, enabling large-scale quantum simulations of the Hubbard model at regimes previously inaccessible, with implications for understanding complex condensed matter phenomena.

Contribution

The authors achieve a several-fold temperature reduction in optical lattice simulations, enabling exploration of strongly-correlated states and new pathways for low-temperature doping regimes.

Findings

Near-saturated antiferromagnetic order at T/t=0.05

Identification of a new low-temperature doping pathway

Comparison of spin correlations with advanced quantum Monte Carlo simulations

Abstract

Ultracold fermionic atoms in optical lattices offer pristine realizations of Hubbard models, which are fundamental to modern condensed matter physics. Despite significant advancements, the accessible temperatures in these optical lattice material analogs are still too high to address many open problems. Here, we demonstrate a several-fold reduction in temperature, bringing large-scale quantum simulations of the Hubbard model into an entirely new regime. This is accomplished by transforming a low entropy product state into strongly-correlated states of interest via dynamic control of the model parameters, which is extremely challenging to simulate classically. At half filling, the long-range antiferromagnetic order is close to saturated, leading to a temperature of $T/t=0.05_{-0.05}^{0.06}$ based on comparisons to numerically exact simulations. Doped away from half-filling, it is exceedingly challenging to realize systematically accurate and predictive numerical simulations. Importantly, we are able to use quantum simulation to identify a new pathway for achieving similarly low temperatures with doping. This is confirmed by comparing short-range spin correlations to state-of-the-art, but approximate, constrained-path auxiliary field quantum Monte Carlo simulations. Compared to the cuprates, the reported temperatures correspond to a reduction from far above to below room temperature, where physics such as the pseudogap and stripe phases may be expected. Our work opens the door to quantum simulations that solve open questions in material science, develop synergies with numerical methods and theoretical studies, and lead to discoveries of new physics.