An experimental and theoretical study was made of electronic spin decoherence in ensembles of nitrogen-vacancy colour centers in bulk high-purity diamond at room temperature. Under appropriate conditions, ensemble nitrogen-vacancy spin coherence times (T2) were found which were comparable to that of a single nitrogen-vacancy with T2 > 600μs for a sample with natural abundance of 13C and paramagnetic impurity density ∼1015/cm3. A sharp decrease was also observed in the coherence time with misalignment of the static magnetic field relative to the nitrogen-vacancy electronic spin axis; consistent with theoretical modelling of nitrogen-vacancy coupling to a 13C nuclear-spin bath. The long coherence times and increased signal-to-noise provided by room-temperature nitrogen-vacancy ensembles were anticipated to aid many applications of nitrogen-vacancy centers in precision magnetometry and quantum information.

Coherence of Nitrogen-Vacancy Electronic Spin Ensembles in Diamond. P.L.Stanwix, L.M.Pham, J.R.Maze, D.Le Sage, T.K.Yeung, P.Cappellaro, P.R.Hemmer, A.Yacoby, M.D.Lukin, R.L.Walsworth: Physical Review B, 2010, 82[20], 201201