  We present a scheme for the implementation of fast arbitrary qubit gates in
the ground state of the negatively charged nitrogen-vacancy (NV$^-$) defect in
diamond. The protocol is especially useful in the low-field regime and for
high-frequency sensing applications. It constitutes an extension to the NV-ERC
technique, which has demonstrated efficient initialization and readout of the
double quantum transition with no leakage to any third level thanks to an
effective Raman coupling. Here we derive a full theoretical framework of the
scheme, identifying the complete unitary associated to the approach, and more
specifically the relevant basis change for each of two characteristic pulse
durations. Based on this insight, we propose a scheme to perform fast qubit
transformations in the double quantum transition. We study its robustness with
respect to pulse-timing errors resulting from faulty identification of system
parameters or phase-control limitations. We finally demonstrate that the
technique can also be implemented in the presence of unknown electric or strain
fields.
