Laser writing of individual nitrogen-vacancy defects in diamond with near-unity yield

Atomic defects in wide-bandgap materials, such as the nitrogen-vacancy (NV) color center in diamond, show considerable promise for the development of a new generation of quantum information technologies, but progress has been hampered by the inability to produce and engineer the defects in a controlled manner. Here, we demonstrate an all-optical method for the deterministic writing of individual NV centers at selected locations with high positioning accuracy. Ultrashort pulse laser processing is used to both create and diffuse defects inside the crystal through local annealing. During the laser-annealing process, online fluorescence feedback provides a trigger to stop processing once the NV formation is detected. This method provides a new tool for the optical fabrication of engineered materials and devices for quantum technologies.