Preparation and coherent manipulation of pure quantum states of a single molecular ion*

We demonstrate control of individual molecules based on quantum-logic spectroscopy [1, 2]. In our experiment, we drive the motional sidebands of Raman transitions in a molecular ion and probe the secular motion with a co-trapped atomic ion. Detection of motional excitation projects the molecule into a pure internal state. The state of the molecule can subsequently be coherently manipulated, as demonstrated by Rabi oscillations between magnetic sublevels of rotational states. We need only one far off-resonant continuous-wave laser to manipulate the molecule. This makes our approach applicable to coherent control and precision measurement of a vast class of molecular ions.\\ \\ \mbox{[1]} C. W. Chou, submitted for publication, arXiv:1612.03926\\ \mbox{[2]} D. Leibfried, New J. Phys. \textbf{14}, 023029 (2012)