Isotopic identification of engineered nitrogen-vacancy spin qubits in ultrapure diamond

Abstract

Nitrogen impurities help to stabilize the negatively-charged-state of NV${}^{-}$ in diamond, whereas magnetic fluctuations from nitrogen spins lead to decoherence of NV${}^{-}$ qubits. It is not known what donor concentration optimizes these conflicting requirements. Here we used 10-MeV ${}^{15}$N${}^{3+}$ ion implantation to create NV${}^{-}$ in ultrapure diamond. Optically detected magnetic resonance of single centers revealed a high creation yield of $40\pm 3$% from ${}^{15}$N${}^{3+}$ ions and an additional yield of $56\pm 3$% from ${}^{14}$N impurities. High-temperature anneal was used to reduce residual defects, and charge stable NV${}^{-}$, even in a dilute ${}^{14}$N impurity concentration of 0.06 ppb were created with long coherence times.