It was recalled that nitrogen–vacancy centres in diamond were a solid-state analogue of trapped atoms, with fine structure in both the ground and excited states that might be used for advanced quantum control. These centres were promising candidates for spin-based quantum information processing and magnetometry at room temperature. Knowledge of the excited-state structure and coherence was critical to evaluating the excited state as a room-temperature quantum resource. Experiments were reported here that probed the excited-state spin-coherence of single nitrogen–vacancy centres. Using a combination of pulsed-laser excitation and nanosecond-scale microwave manipulation, excited-state Rabi oscillations were observed, and multi-pulse resonant control permited the study of coherent excited-state electron/nuclear-spin interactions. In order to understand these processes, a finite-temperature theory of excited-state spin dynamics was developed that also provided a path towards the engineering of longer excited-state spin coherence.

Excited-State Spin Coherence of a Single Nitrogen–Vacancy Centre in Diamond. G.D.Fuchs, V.V.Dobrovitski, D.M.Toyli, F.J.Heremans, C.D.Weis, T.Schenkel, D.D.Awschalom: Nature Physics, 2010, 6, 668–72