  Single dopant atoms or dopant-related defect centers in a solid state matrix
provide an attractive platform for quantum simulation of topological states,
for quantum computing and communication, due to their potential to realize a
scalable architecture compatible with electronic and photonic integrated
circuits. The production of such quantum devices calls for deterministic single
atom doping techniques because conventional stochastic doping techniques are
cannot deliver appropriate architectures. Here, we present the fabrication of
arrays of praseodymium color centers in YAG substrates, using a deterministic
source of single laser-cooled Pr$^+$ ions. 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 up to 50%
and realizing a placement accuracy of better than 50 nm.
