Fig. 3: Two-axis control with varying initializations.
From: Universal quantum control of an atomic spin qubit on a surface
a Pulse sequence for two-axis control of a spin qubit where the phase φ of the second pulse (purple) is swept between 0 and 2π. Four simulated trajectories of the qubit’s final state (with respect to φ) are illustrated on the Bloch sphere, corresponding to different specific choices of the rotation Ωτ of the first pulse (red). b ESR signals measured with the sequence in a for 7 different Ωτ (labeled at right side) (VDC = 50 mV, IDC = 4 pA, VRF = 120 mV). Solid curves are cosine functions \(\Delta I={-I}_{0}{\rm{\cos }}\varphi\). Both data and fits are vertically shifted for clarity. c \({I}_{0}\) as a function of \(\varOmega \tau\), extracted from the fits of 13 curves (including those in b, complete data set is shown in Supplementary Fig. 8). Error bars denote the 95% confidence intervals of the cosine fits. Solid curve is a sinusoidal fit. Duration of the \({\rm{\pi }}/2\) pulses is ~ 6 ns.
