Stopping light, playing with it, then releasing it.

[Topher925]

"Now it's at a crawl, and we can actually stop it—keep light bottled up entirely inside the BEC, look at it, play with it and then release it when we're ready."

A quote from an article published by Smithsonian Magazine: http://www.smithsonianmag.com/science-nature/phenom-200801.html?c=y&page=1

I know this article is almost a year old, but I have never heard of this before. I also find this pretty amazing and seems to me that some one such as myself should have read this was possible from somewhere already.

So...how exactly is this done, does anyone know? Is this something that can be predicted by quantum electrodynamics? I always thought light was just the creation and destruction of photons, like the feeling of cold just being heat transferring from your body. Are they just taking photons and just stopping them in matter? And one more thing, does the probability of determining the position of an electron greatly increase at near absolute zero temperatures?

 

[Andy Resnick]

The concept is that the BEC (for example) has a very large dispersion. This type of phenomenon occurs near absorption peaks, and essentially the refractive index becomes extremely large- thus the 'speed of light' becomes very small. It's conceptually similar to anamolous dispersion effects.

Now to 'stop' the propogation of light, experiments were performed to *coherently* encode the electromagnetic field as an atomic spin state. In that case, the interpretation is that the light was 'stopped' and 'released'. That's different than absorption- absorption is an incoherent process, all information contained in the electromagnetic field is destroyed upon absorption.

There's other, similar, experiments- using a highly scattering powder can create closed loops for light to propagate around, for example.

 

[ZapperZ]

Nothing better than getting from the "horse's mouth" itself. So read this article by Lene Hau, who is THE major player in this particular area.

http://physicsworld.com/cws/article/print/20

Zz.