Resolved-sideband laser cooling in a Penning trap

TL;DR

This paper demonstrates near-perfect laser cooling of a single calcium ion in a Penning trap to its motional ground state, with very low heating rates, advancing quantum control in ion traps.

Contribution

It reports the first successful resolved-sideband laser cooling of a single ion in a Penning trap to the motional ground state.

Findings

98% ground state occupation achieved

Very low heating rate of approximately 0.3 quanta per second

Effective cooling in a strong binding regime

Abstract

We report the laser cooling of a single $^{40}\text{Ca}^+$ ion in a Penning trap to the motional ground state in one dimension. Cooling is performed in the strong binding limit on the 729-nm electric quadrupole $S_{1/2}\leftrightarrow D_{5/2}$ transition, broadened by a quench laser coupling the $D_{5/2}$ and $P_{3/2}$ levels. We find the final ground state occupation to be $98\pm1\%$. We measure the heating rate of the trap to be very low with $\dot{\bar{n}}\approx 0.3\pm0.2\textrm{s}^{-1}$ for trap frequencies from $150-400\textrm{kHz}$, consistent with the large ion-electrode distance.