Figure 1: Device layout and quadrupole broadening.
From: Quadrupolar and anisotropy effects on dephasing in two-electron spin qubits in GaAs
(a) Gates used for pulsed qubit control are depicted in blue; the energy of the conduction band edge ECB is shown on the left. (b) Nuclear spins 3/2 with magnetic moment μ in the proximity of the quantum dot experience quadrupolar coupling with electric field gradients Vx′x′ induced by crystal distortion due to the electric field of the triangular quantum well. (c) While the centre transition, with splitting ω0, stays unchanged, the satellite transitions, distorted by the electron’s own charge, exhibit a quadrupolar shift by ωQ. (d) The resulting frequency distribution F(ω) consists of two Gaussians with different variances, one showing an excess quadrupolar broadening of δωQ. (e) Echo amplitude for magnetic fields along the [110] axis, showing oscillations with the relative Larmor frequencies of the three nuclear spins. A semi-classical model (solid line) is used to fit the data (dots, offset for clarity).
