Tool sketches quantum circuits

Computer chips are manufactured using photo lithography -- a technique that employs light and chemicals to etch microscopic features into silicon.

Researchers routinely use electron beam lithography, which uses beams of electrons instead of photons, to etch even smaller devices, like the quantum dots that trap single electrons to form the building blocks of quantum computers.

Electron beam lithography is a very slow process, however.

Researchers from Cambridge University in England and the Massachusetts Institute of Technology have developed a lithographic technique, dubbed erasable electrostatic lithography, that allows a quantum device to be drawn in a few hours rather than a couple of weeks.

The researchers modified a scanning tunneling microscope so that they could sketch charge patterns onto the surface of a piece of the semiconductor gallium arsenide and erase the patterns using red light. The surface charge, which draws from a subsurface sheet of electrons, defines working quantum components.

The researchers have used the method to define quantum wires, dots and hills, and are currently working on improving the technique's resolution, according to the researchers.

The method could be used practically in five years, according to the researchers. The work appeared in the August 14, 2003 issue of Nature.