Speed-of-light computing comes a step closer

Computers that operate at the speed of light have come a step closer.Researchers have devised a light-based transistor made of semiconducting nanowires that could be a key building block of machines that are hundreds of times faster than today's supercomputers.Until now,optical transistors,in which one beam of light controls the state of another,have required large bursts of photons to switch states,making them unfeasibly power-hungry. Now Mikhail Lukin and colleagues at Harvard University have come up with a technique that uses a single photon to switch the state of a light beam.This is the first workable suggestion for building an optical computer,they say.An electrical transistor's speed is limited by the speed at which an electric current flows.In theory,because photons travel much faster than an electric current, substituting photons for electrons would speed things up.In reality,however,finding the optical equivalent of a transistor has proved difficult.Like an electric current,light can be pulsed on or off. The difficulty arises in controlling the switch between these two states.Unlike electrons, whose flow can be controlled by an electric field, photons are electrically neutral and do not normally interact with each other.This makes it hard to use one light beam to control another...
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As in the days of Noah...