  The nuclear spin in the vicinity of a nitrogen-vacancy (NV) center possesses
of long coherence time and convenient manipulation assisted by the strong
hyperfine interaction with the NV center. It is suggested for the subsequent
quantum information storage and processing after appropriate initialization.
However, current experimental schemes are either sensitive to the inclination
and magnitude of the magnetic field or require thousands of repetitions to
achieve successful realization. Here, we propose polarizing a 13C nuclear spin
in the vicinity of an NV center via a dark state. We demonstrate theoretically
that it is robust to polarize various nuclear spins with different hyperfine
couplings and noise strengths.
