  Arrays of identical and individually addressable qubits lay the foundation
for the creation of scalable quantum hardware such as quantum processors and
repeaters. Silicon vacancy centers in diamond (SiV) offer excellent physical
properties such as low inhomogeneous broadening, fast photon emission, and a
large Debye-Waller factor, while the possibility for all-optical ultrafast
manipulation and techniques to extend the spin coherence times make them very
promising candidates for qubits. Here, we have developed arrays of nanopillars
containing single SiV centers with high yield, and we demonstrate ultrafast
all-optical complete coherent control of the state of a single SiV center. The
high quality of the chemical vapor deposition (CVD) grown SiV centers provides
excellent spectral stability, which allows us to coherently manipulate and
quasi-resonantly read out the state of individual SiV centers on picosecond
timescales using ultrafast optical pulses. This work opens new opportunities
towards the creation of a scalable on-chip diamond platform for quantum
information processing and scalable nanophotonics applications.
