  Nuclear spins in the solid state environment of diamond are highly coherent,
but difficult to rapidly control due to the small nuclear gyromagnetic ratio.
Here we demonstrate a more than 50-fold enhancement of the effective nuclear
gyromagnetic ratio by coupling the nuclear spin to an electronic spin of a
nitrogen-vacancy (NV) center in diamond. The enhancement allows for faster
nuclear spin rotations and is in good agreement with second-order perturbation
theory. The method may be applied to other systems with similar
electron-nuclear spin interactions, such as phosphorous donors in silicon,
opening up the possibility of fast and direct nuclear spin control in coupled
spin systems.
