3D Sisyphus Cooling of Trapped Ions

TL;DR

This paper demonstrates 3D Sisyphus cooling of trapped $^{171}$Yb$^+$ ions, achieving significant reduction in motional energy and enabling more efficient sideband cooling, with detailed characterization and comparison to simulations.

Contribution

It introduces a method for 3D Sisyphus cooling of trapped ions and characterizes its effectiveness compared to existing cooling techniques.

Findings

Achieved mean motional energy of 1-3 quanta for four ions

Reduced energy by approximately an order of magnitude below Doppler cooling

Enabled more efficient subsequent sideband laser cooling

Abstract

Using a laser polarization gradient, we realize 3D Sisyphus cooling of $^{171}$Yb$^+$ ions confined in and near the Lamb-Dicke regime in a linear Paul trap. The cooling rate and final mean motional energy of a single ion are characterized as a function of laser intensity and compared to semiclassical and quantum simulations. Sisyphus cooling is also applied to a linear string of four ions to obtain a mean energy of 1-3 quanta for all vibrational modes, an approximately order-of-magnitude reduction below Doppler cooled energies. This is used to enable subsequent, efficient sideband laser cooling.