Coherence of nitrogen-vacancy electronic spin ensembles in diamond

Abstract

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 $({T}_{2})$ comparable to that of single NV with ${T}_{2}>600\text{ }\ensuremath{\mu}\text{s}$ for a sample with natural abundance of $^{13}\text{C}$ and paramagnetic impurity density $\ensuremath{\sim}{10}^{15}\text{ }{\text{cm}}^{\ensuremath{-}3}$. 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 $^{13}\text{C}$ 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.