  Carbon implantation at the nanoscale is highly desired for the engineering of
defect-based qubits in a variety of materials, including silicon, diamond, SiC
and hBN. However, the lack of focused carbon ion beams does not allow for the
full disclosure of their potential for application in quantum technologies.
Here, we develop and use a carbon source for focused ion beams for the
simultaneous creation of two types of quantum emitters in silicon, the W and G
centers. Furthermore, we apply a multi-step implantation protocol for the
programmable activation of the G centers with sub-100- nm resolution. This
approach provides a route for significant enhancement of the creation yield of
single G centers in carbon-free silicon wafers. Our experimental demonstration
is an important step towards nanoscale engineering of telecom quantum emitters
in silicon of high crystalline quality and isotope purity.
