Single dopant atoms or dopant-related defect centers in a solid state
matrix are of particular importance among the physical systems proposed
for quantum computing and communication, due to their potential to
realize a scalable architecture compatible with electronic and photonic
integrated circuits. Here, using a deterministic source of single
laser-cooled Pr+
ions, we present the fabrication of arrays of praseodymium color
centers in yttrium-aluminum-garnet substrates. The beam of single Pr+
ions is extracted from a Paul trap and focused down to 30(9) nm. Using a
confocal microscope, we determine a conversion yield into active color
centers of up to 50% and realize a placement precision of 34 nm.