Electrically tunable hole g factor of an optically active quantum dot for fast spin rotations

We report a large g factor tunability of a single hole spin in an InGaAs quantum dot via an electric field. The magnetic field lies in the in-plane direction x, the direction required for a coherent hole spin. The electrical field lies along the growth direction z and is changed over a large range, 100 kV/cm. Both electron and hole g factors are determined by high resolution laser spectroscopy with resonance fluorescence detection. This, along with the low electrical-noise environment, gives very high quality experimental results. The hole g factor g(h)(x) depends linearly on the electric field F-z, dg(h)(x)/dF(z) = (8.3 +/- 1.2) x 10(-4) cm/kV, whereas the electron g factor g(e)(x) is independent of electric field dg(e)(x)/dF(z) = (0.1 +/- 0.3) x 10(-4) cm/kV (results averaged over a number of quantum dots). The dependence of g(h)(x) on F-z is well reproduced by a 4 x 4 k . p model demonstrating that the electric field sensitivity arises from a combination of soft hole confining potential, an In concentration gradient, and a strong dependence of material parameters on In concentration. The electric field sensitivity of the hole spin can be exploited for electrically driven hole spin rotations via the g tensor modulation technique and based on these results, a hole spin coupling as large as similar to 1 GHz can be envisaged.