Coherence of nitrogen-vacancy electronic spin ensembles in diamond
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We present an experimental and theoretical study of electronic spin decoherence in ensembles of nitrogen-vacancy (NV) color centers in bulk high-purity diamond at room temperature. Under appropriate conditions, we find ensemble NV spin coherence times (T2) comparable to that of single NV with T2 >600s for a sample with natural abundance of C 13 and paramagnetic impurity density 1015 cm-3. We also observe a sharp decrease in the coherence time with misalignment of the static magnetic field relative to the NV electronic spin axis, consistent with theoretical modeling of NV coupling to a C 13 nuclear-spin bath. The long coherence times and increased signal-to-noise provided by room-temperature NV ensembles will aid many applications of NV centers in precision magnetometry and quantum information. 2010 The American Physical Society.