University of New South Wales (UNSW) researchers have developed a transistor from a single phosphorus atom placed in a silicon crystal. The researchers say the breakthrough could lead to a future quantum computer with superior computing efficiency. "This is the first time anyone has shown control of a single atom in a substrate with this level of precise accuracy," says UNSW professor Michelle Simmons. The device has tiny markers etched onto its surface so metal contacts can be connected to apply a voltage. "Our group has proved that it is really possible to position one phosphorus atom in a silicon environment--exactly as we need it--with near-atomic precision, and at the same time register gates," Simmons says. The researchers used a scanning tunneling microscope to manipulate atoms at the surface of the crystal inside an ultra-high-vacuum chamber. The researchers patterned phosphorus atoms into functional devices on the crystal and then covered them with a non-reactive layer of hydrogen, using a lithographic process. Finally, the device was surrounded by a silicon layer, and it contacted electrically using a system of markers on the silicon chip to align metallic connects.