  Spins of negatively charged nitrogen-vacancy (NV$^-$) defects in diamond are
among the most promising candidates for solid-state qubits. The fabrication of
quantum devices containing these spin-carrying defects requires
position-controlled introduction of NV$^-$ defects having excellent properties
such as spectral stability, long spin coherence time, and stable negative
charge state. Nitrogen ion implantation and annealing enable the positioning of
NV$^-$ spin qubits with high precision, but to date, the coherence times of
qubits produced this way are short, presumably because of the presence of
residual radiation damage. In the present work, we demonstrate that a high
temperature annealing at 1000$^\circ$C allows 2 millisecond coherence times to
be achieved at room temperature. These results were obtained for
implantation-produced NV$^-$ defects in a high-purity, 99.99% $^{12}$C enriched
single crystal chemical vapor deposited diamond. We discuss these remarkably
long coherence times in the context of the thermal behavior of residual defect
spins. [Published in Physical Review B {\bf{88}}, 075206 (2013)]
