An innovative system, which works rather like a child's Etch A Sketch toy, could significantly speed the design of quantum electronic devices. The intricate circuits needed can be "drawn" on a surface using tiny spots of charge, adjusted, and then scrubbed out with a flash of light. Rolf Crook and colleagues at Cambridge University, UK, who developed the technique, have already built minute electrical circuits that they are using to study quantum effects. These include nanowires, point contacts - narrow junctions between reservoirs of charge - and isolated islands of charge called quantum dots. "The beauty of this is they can draw a device, then modify it a bit, and then modify it a bit more and see how the characteristics change with the shape. That is very powerful," says Ray Ashoori, an expert in quantum effects in semiconductors at MIT in Cambridge, Massachusetts. Typically, such small-scale devices are constructed by "lithography". This process uses an electron beam to carve delicate patterns into a polymer layer on a semiconductor wafer, which then serves as a stencil for metal electrodes. Full article here.