Fig. 3. Spin rotation and full coherent control.

a Excitation pulsed sequence. A non-resonant pulse first injects carriers into the QD followed by a pump pulse which initialises the spin into $∣\uparrow ⟩$. Two circularly polarised ps-pulses with time delay Δτ rotate the electron’s spin. A resonant readout pulse is used to probe any population remaining in the $∣\downarrow ⟩$ state. b Pictorial representation of the electron qubit evolution along the Bloch sphere. c Integrated emission intensity as a function of a single rotation pulse power, at 9 T, for three different red-detunings from the lowest energy transition, demonstrating coherent control of the electron’s spin. The data are fitted to extract the power values at angles θ = mπ/2 ∀m ∈ 1, 2, 3, 4, 5, 6, as marked by the error-barred squares (95% confidence interval). d Rotation angle versus pulse power fit results in an average power dependence of $\theta \propto P_{rot}^{0.77}$ for the three detunings. e Ramsey interference for a pair of rotation pulses, at 5 T, red detuned by Δλ = 0.6 nm from the lowest energy transition, showing normalised integrated emission counts as a function of the time delay between the pulses. f Full coherent control of the spin-qubit at 5 T. Normalised integrated emission counts as a function of rotation angle θ and time delay between the rotation pulses.