HANDS ON GUIDE

4 - Optical computing

Because electrons are just too slow

WHAT IS IT?

One of the fundamental limitations on the speed data can travel through a computer is the speed at which electrons flow. As all computers use electricity to encode binary information, the data can arrive no faster than the electrons can get there. One way of overcoming this limitation is to use light, rather than electricity, to carry data. According to IBM, transmitting data optically will be 100 times faster than using electrons, but use 10 times less power. Just as fiber-optics have revolutionised the volume of data that can be sent via the Internet, optical data transfer inside an individual chip could allow for much faster computations.

HOW DOES IT WORK?

Building an optical computer means replacing the transistors that form the basis of electronic switching with something that can do the same thing with beams of light. Electronic circuits made from silicon are extremely efficient at allowing electrons to move around a computer. Finding a material to replace silicon transistors is a difficult task. Researchers at Harvard University used a 'plasmon', a kind of photonic membrane that controls the intensity of light that is emitted (on a very small scale) making it the rough equivalent of a transistor.

Earlier this year, a lowly beetle from South America gave scientists clues as to how to build an efficient optical computer. Its green scales have a unique property - their molecular structure makes the perfect photonic crystal.

WHAT COULD GET IN THE WAY?

There are many different problems to be overcome before an optical computer can be built. Not only must materials be invented to allow a processor to make calculations using light, but a modulator is needed to be placed within an electronic circuit and convert electrical pulses to light beams. Any optical chip would be likely to use a combination of photons and electrons to transfer data, and would need a way to switch between the two. IBM announced at the end of 2007 that it made a breakthrough in researching these modulators.

ETA

20 years. Breakthroughs will almost certainly happen over the next five years, but nothing will be ready for home computing for a long time.

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