This "neither here nor there" quantum state is what can be
controlled in this new molecule simply by altering the voltage
of the transistor. Until now, the challenge had been to create a
computer semiconductor in which the quantum state could be
controlled, creating a qubit. "If you want to build a quantum
computer you have to be able to control the occupancy of the
quantum states," Klimeck says. "We can control the location of
the electron in this artificial atom and, therefore, control the
quantum state with an externally applied electrical field." The
discovery began when Sven Rogge and his colleagues at Delft
University of Technology in the Netherlands were experimenting
with nano-scale transistors that show the effects of
unintentional impurities, or dopants. The researchers found
properties in the current-voltage characteristics of the
transistor that indicated electrons were being transported by a
single atom, but it was unclear what impurity was causing this
effect. Physicist Lloyd Hollenberg and coll