  Initializing a set of qubits to a given quantum state is a basic prerequisite
for the physical implementation of quantum-information protocols. Here, we
discuss the polarization of the electronic and nuclear spin in a single
nitrogen vacancy center in diamond. Our initialization scheme uses a sequence
of laser, microwave and radio-frequency pulses, and we optimize the pumping
parameters of the laser pulse. A rate equation model is formulated that
explains the effect of the laser pulse on the spin system. We have
experimentally determined the population of the relevant spin states as a
function of the duration of the laser pulse by measuring Rabi oscillations and
Ramsey-type free-induction decays. The experimental data have been analyzed to
determine the pumping rates of the rate equation model.
