Dark resonances as a probe for the motional state of a single ion
Résumé
Single, rf-trapped ions find various applications ranging from metrology to quantum computation. High-resolution interrogation of an extremely weak transition under best observation conditions requires an ion almost at rest. To avoid line-broadening effects such as the second order Doppler effect or rf heating in the absence of laser cooling, excess micromotion has to be eliminated as far as possible. In this work the motional state of a confined three-level ion is probed, taking advantage of the high sensitivity of observed dark resonances to the trapped ion's velocity. The control of the excess micromotion is tested by monitoring the dark resonance contrast with varying laser beam geometry. The influence of different parameters such as laser linewidth and power has been investigated experimentally and numerically.