Coherence of nitrogen-vacancy electronic spin ensembles in diamond

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 (T[superscript 2]) comparable to that of single NV with T[superscript 2]>600 μs for a sample with natural abundance of [superscript 13]C and paramagnetic impurity density ~10[superscript 15] cm[superscript −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 [superscript 13]C 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.National Science Foundation (U.S.)United States. Defense Advanced Research Projects Agency (DARPA)National Institute of Standards and Technology (U.S.