  Hybrid quantum registers consisting of different types of qubits offer a
range of advantages as well as challenges. The main challenge is that some
types of qubits react only slowly to external control fields, thus considerably
slowing down the information processing operations. One promising approach that
has been tested in a number of cases is to use indirect control, where external
fields are applied only to qubits that interact strongly with resonant
excitation pulses. Here we use this approach to indirectly control the nuclear
spins of an NV center, using microwave pulses to drive the electron spin,
combined with free precession periods optimized for generating logical gate
operations on the nuclear spins. The scheme provides universal control and we
present two typical applications: polarizing the nuclear spin and measuring
nuclear spin free induction decay signals, both without applying
radio-frequency pulses. This scheme is versatile as it can be implemented over
a wide range of magnetic field strengths and at any temperature.
