Fig. 4: Coherent control of the electronic spin qubit.

a For optically detected magnetic resonance spectroscopy, the spin is initialized before a microwave (MW) pulse is applied, followed by an optical readout sequence (see inset). The splitting into three lines, each with a FWHM of 2.37(2) MHz (solid Gaussian fit curve), is attributed to the coupling to proximal ²⁹Si nuclear spins. b The spin population undergoes Rabi oscillations as a function of the MW pulse duration, both on resonance with the central peak (red) and one of the side peaks (orange). The Rabi frequency extracted from an exponentially decaying sine fit allows determining the spectral width of the pulses applied in panel a (colored areas). c The spin coherence time is measured by applying a three-pulse spin-echo sequence (inset). The echo amplitude decreases with increasing sequence length and is well-fit with a Gaussian decay from which T₂ = 48(2) μs is obtained at a temperature of 2.75 K (bright red). At 4.45 K, a reduced value of T₂ = 23(1) μs is observed (dark red). Error bars: 1 SD.