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 colleagues at the University of Melbourne in Australia were able to construct a theoretical silicon-based quantum computer chip based on the concept of using an individual impurity.
"The team found that the measurements only made sense if the molecule was considered to be made of two parts," Hollenberg says. "One end comprised the arsenic atom embedded in the silicon, while the 'artificial' end of the molecule forms near the silicon surface of the transistor. A single electron was spread across both ends.
"What is strange about the 'surface' end of the molecule is that it occurs as an artifact when we apply electrical current across the transistor and hence can be considered 'manmade.'
|Contact: Steve Tally|