[Lurker]

How does one cool something to 'near absolute zero' with a laser?

L

[SF Republican]

How does one cool something to 'near absolute zero' with a laser?
If it is zero degrees and it gets twice as cold, how cold is it?

[Redcloak]

You have to think about what "heat" really is. It's the measure of how much atoms are vibrating. The lasers push on the ion from opposite directions and hold it in place. This stops it from vibrating. No vibration, no heat. And for their purposes, no vibration means no Doppler shifts in the emitted light. All of the photons come from the same place and from something that isn't moving.

Light from a vibrating source is spectrally broadened by Doppler shifting. Imagine the old train-blowing-its-whistle-as-it-approaches analogy for Doppler shifting. Now imagine that the train isn't coming toward you; it's simply vibrating back and forth along the track. The whistle, rather than having a single, clear tone, will sound fuzzier as the tone smears out to different frequencies. The same thing happens with light. A laser should have a single wavelength; but, since the atoms inside the laser are hot, they vibrate and broaden the colors of the laser to other, nearby wavelengths (frequencies). Some are coming toward you and look "bluer" while some are going away and look "redder". If you are trying to use the light as a clock source, then the frequency is constantly changing. This clock avoids that by chilling the emitter.

[arthurus]

Probably with a microwave referigerator.