Isotope-agnostic motional ground-state cooling of neutral Yb atoms

TL;DR

This paper demonstrates isotope-agnostic motional ground-state cooling of neutral Yb atoms in optical lattices using a chirped sideband cooling scheme, achieving high ground-state fractions and low motional occupation numbers, advancing quantum simulation and computing.

Contribution

The work introduces a generalized, isotope-agnostic cooling method with high efficiency in 2D and 3D optical lattices, suitable for bosonic and fermionic Yb atoms, enabling new quantum applications.

Findings

Achieved 97% ground-state fraction for 171Yb in 2D lattices.

Reached an average motional occupation of 0.015 for 171Yb.

Demonstrated effective cooling in 3D lattices with occupation 0.15.

Abstract

Efficient high-fidelity ground-state cooling of motional degrees of freedom is crucial for applications in quantum simulation, computing and metrology. Here, we demonstrate direct ground-state cooling of fermionic $^{171}$Yb and bosonic $^{174}$Yb atoms in two- and three-dimensional magic-wavelength optical lattices on the ultranarrow clock transition. Its high spectral resolution offers the potential for reaching extremely low temperatures. To ensure efficient cooling, we develop a chirped sideband cooling scheme, where we sweep the clock-laser frequency to mitigate the effects of spatial trap inhomogeneities. We further generalize the theoretical description of sideband spectra to higher-dimensional lattices for precise thermometry. We achieve 2D ground state fractions of $97\%$ for $^{171}$Yb with an average motional occupation of $\bar{n}\simeq0.015$ and provide a direct comparison with $^{174}$Yb, reaching similar cooling performance. Applying the same scheme in 3D results in $\bar{n}\simeq0.15$ limited by layer-to-layer inhomogeneities in the vertical direction. These results demonstrate efficient motional ground-state cooling in optical lattices, especially for bosonic alkaline-earth(-like) atoms, where other methods are not applicable, opening the door to novel protocols for quantum science applications with neutral atoms.