A neutral-atom Hubbard quantum simulator in the cryogenic regime.

Abstract

Ultracold fermionic atoms in optical lattices offer pristine realizations of Hubbard models¹, which are fundamental to modern condensed-matter physics^2,3. Despite notable advancements^4-6, the accessible temperatures in these optical lattice material analogues are still too high to address many open problems^7-10. Here we demonstrate a several-fold reduction in temperature^6,11-13, 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^14,15, which is extremely challenging to simulate classically¹⁰. At half-filling, the long-range antiferromagnetic order is close to saturation, leading to a temperature of <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>T</mi> <mo>/</mo> <mi>t</mi> <mo>=</mo> <mn>0.0</mn> <msubsup><mrow><mn>5</mn></mrow> <mrow><mo>-</mo> <mn>0.05</mn></mrow> <mrow><mo>+</mo> <mn>0.06</mn></mrow> </msubsup> </mrow> </math> based on comparisons with numerically exact simulations. Doped away from half-filling, it is exceedingly challenging to realize systematically accurate and predictive numerical simulations⁹. 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^16-18. Compared with the cuprates^2,19,20, the reported temperatures correspond to a reduction from far above to below room temperature, at which physics such as the pseudogap and stripe phases may be expected^3,19,21-24. 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^8,10.