Friday, December 16, 2005

Slow light again

Remember Mercury Delay lines ? No, I wasn't there at the time, but it's an odd bit of technology that hackers like to tell one another about. The UNIVAC I (and other early computers) used this technique to store electronic pulses of information to be used later. The basic idea (and metaphor to be emulated) is that you find a way to send bits out on a slow loop so they'll return at a known time in the future when you'll be ready to use them again. Originally used in WWII radar to remove static objects from images, they were eventually used as generic (short-term) memory.

Well there's new work on slowing down the speed of light that may bring this metaphor in reach again. Remember in 1999, when scientists used clouds of ultracold sodium gas in a Bose-Einstein condensate to slow light down to "walking speed"? Well, the current work uses a silicon crystal full of holes to slow the light. When they send small currents through the crystal, temperature changes in the crystal vary the delay that is applied to the passing light. This means they can vary the delay, making the delay lines more versatile.

Everything Old is New Again.

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