Rapid cooling of the in-plane motion of two-dimensional ion crystals in a Penning trap to millikelvin temperatures

The authors propose a readily implementable technique for the efficient cooling of low-frequency planar motion in large two-dimensional ion crystals in Penning traps. The approach enables rapid cooling to millikelvin temperatures within a few milliseconds, paving the way for sub-Doppler laser cooling and improved quantum information experiments with two-dimensional trapped ion crystals.