Phys. Res. Lett. 101, 130501 (2008)

Credit: N. C. MENICUCCI ET AL./PHYS. REV. LETT.

Schemes for quantum computing abound, but most intend to carry out computations on objects such as atoms. Now Nicolas Menicucci at Princeton University in New Jersey and his colleagues propose a method that uses a rainbow of colours.

The group suggests firing lasers of 15 different frequencies into a cavity with a mirror at each end. Inside the cavity, a crystal splits each laser's photons into quantum mechanically 'entangled' pairs. Those pairs, in turn, become entangled with photons from the other lasers. The resulting cobweb of entangled photons could be visualized as a brightly coloured tube (pictured).

The authors would be able to manipulate their rainbow computer by measuring the entangled photons that escape from the cavity — and the computer could, in theory, perform any computation.