Near ground-state cooling of two-dimensional trapped-ion crystals with more than 100 ions

TL;DR

This paper demonstrates near ground-state cooling of over 100 ions in a 2D crystal, achieving rapid, sub-Doppler cooling of all modes, which enhances quantum information and metrology applications.

Contribution

It provides the first experimental demonstration of near ground-state cooling of large 2D ion crystals with over 100 ions, using electromagnetically induced transparency cooling.

Findings

Sub-Doppler cooling achieved for all drumhead modes.

Center-of-mass mode cooled to near ground state with $ar{n} = 0.3\, ext{±}\,0.2$.

Cooling rate exceeds single particle predictions, aligning with many-body theory.

Abstract

We study, both experimentally and theoretically, electromagnetically induced transparency cooling of the drumhead modes of planar 2-dimensional arrays with up to $N\approx 190$ Be${}^+$ ions stored in a Penning trap. Substantial sub-Doppler cooling is observed for all $N$ drumhead modes. Quantitative measurements for the center-of-mass mode show near ground state cooling with motional quantum numbers of $\bar{n} = 0.3\pm0.2$ obtained within $200~\mu s$. The measured cooling rate is faster than that predicted by single particle theory, consistent with a quantum many-body calculation. For the lower frequency drumhead modes, quantitative temperature measurements are limited by apparent damping and frequency instabilities, but near ground state cooling of the full bandwidth is strongly suggested. This advancement will greatly improve the performance of large trapped ion crystals in quantum information and quantum metrology applications.