How Many Photons Can Dance On The Head Of A Chip?

Quantum Physics doesn't get much weirder than this: When two subatomic particles enjoy a brief encounter, their fates stay coupled. Whatever happens to one is instantly mirrored by its mate--even if at opposite ends of the galaxy. Physicists call this phenomenon "entanglement." Although Albert Einstein could never accept it as real, numerous experiments have confirmed it. Now some scientists believe entanglement might be the answer to chipmakers' prayers.

A transatlantic team led by Jonathan P. Dowling, a senior researcher at NASA's Jet Propulsion Laboratory, figures entanglement can help pack chips with ever-smaller circuit lines, way beyond the infinitesimal 0.1-micron width that may be the brick wall for today's technology. That limit should be reached shortly after 2005.

The lines on advanced chips now are printed with ultraviolet light that has a wavelength of 248 nanometers. Normally, light can't reliably produce lines thinner than half its wavelength--in this case 0.124 microns--because the photons scatter in the air. But pump the light through a crystal that pairs up the photons, Dowling predicts, and the same equipment could write 0.06-micron lines. That's because the photons virtually "talk to each other and conspire to arrive at almost the same spot" on the silicon, he says. Since entanglement can link up multiple photons, it may be possible to write even finer lines. A trio, for instance, could print 0.04-micron lines. Dowling's crew is gearing up to test their theory in real-life experiments.

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