Spin lifetimes and g-factor tuning in Si/SiGe quantum wells

We show that (i) the spin life times of electrons in SiGe quantum wells are much longer than the spin manipulation times required for pulsed ESR under realistic conditions. We demonstrate also (ii) that the g-factor depends on angle, Ge-content and on the kinetic energy of free carriers. The latter two dependencies are sufficiently strong to permit individual manipulation in a controlled NOT gate by clearly separated resonance conditions.