Fig. 3
SU(2) control over the rotation axis. a Rabi oscillations as a function of \(\delta\), at a bare Rabi frequency \(\Omega =120\ {\rm{MHz}}\). \(\delta\) dictates the polar angle \(\theta =\arctan (\frac{\Omega }{\delta })\) of the Rabi vector. b Dependence of the \(\left|\downarrow \right\rangle\)-state population on the relative phase \(\phi\) of two immediately consecutive \(13\ {\rm{MHz}}\,\frac{\pi }{2}\)-pulses, as \({\phi }_{\mathrm {{\mu {w}}}}\) is varied between \([0,2\pi ]\). This phase corresponds to the azimuthal angle of the Rabi vector. The phase offset between maximum readout signal and constructive pulse interference is consistent with a systematic detuning of \(3.5\ {\rm{MHz}}\). c Ramsey interferometry on the electron. Two \(24\ {\rm{MHz}}\ \frac{\pi }{2}\)-pulses, separated by a delay \(\tau\) and followed by a readout of the \(\left|\downarrow \right\rangle\) (\(\left|\uparrow \right\rangle\)) state produce the pink (purple) data points. These data are fitted by a Gaussian envelope, \(\rho (t)=\frac{{\rho }_{0}}{2}(1\pm {{\mathrm {e}}}^{-{(t/{T}_{2}^{* })}^{2}})\) for an initial population \({\rho }_{0}\), yielding a \(47.4\,(47.1)\)-\({\rm{ns}}\) inhomogeneous dephasing time for the upper (lower) curve
