  Silicon-based quantum emitters are candidates for large-scale qubit
integration due to their single-photon emission properties and potential for
spin-photon interfaces with long spin coherence times. Here, we demonstrate
local writing and erasing of selected light-emitting defects using fs laser
pulses in combination with hydrogen-based defect activation and passivation. By
selecting forming gas (N2/H2) during thermal annealing of carbon-implanted
silicon, we form Ci centers while passivating the more common G-centers. The Ci
center is a telecom S-band emitter with very promising spin properties that
consists of a single interstitial carbon atom in the silicon lattice. Density
functional theory calculations show that the Ci center brightness is enhanced
by several orders of magnitude in the presence of hydrogen. Fs-laser pulses
locally affect the passivation or activation of quantum emitters with hydrogen
and enable programmable quantum emitter formation in a qubit-by-design
paradigm.
