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.
Categories: physics.atom-ph quant-ph