"People have already built small quantum computers," said researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer but a connected cluster of small ones."
According to the group, distributing quantum information on a bridge, or network, could also enable novel forms of quantum sensing, since quantum correlations allow all the atoms in the network to behave as though they were one single atom.
The researchers used a focused ion beam implanter designed for blasting single ions into precise locations on a diamond substrate. They used implantation to replace one carbon atom of the diamond with the larger silicon atom, which causes the two carbon atoms on either side of the silicon atom to flee. This leaves the silicon atom buffered against stray electrical currents by the neighbouring non-conducting vacancies.
"What we've done is implant the silicon atoms exactly where we want them," said Camacho. "We can create thousands of implanted locations, which all yield working quantum devices, because we plant the atoms well below the surface of the substrate and anneal them in place. Before this, researchers had to search for emitter atoms among about 1000 randomly occurring defects – that is, non-carbon atoms – in a diamond substrate of a few microns to find even one that emitted strongly enough to be useful at the single photon level."
Once the silicon atoms are settled in the diamond substrate, laser-generated photons bump silicon electrons into their next higher atomic energy state; when the electrons return to the lower energy state, they eject quantised photons that carry information through their frequency, intensity and the polarisation of their wave.
The researchers developed special detectors – metal films atop the diamond substrate – that showed the ion beam implants were successful by measuring the ionisation signal produced by single ions.