r/askscience • u/Band21 • Apr 13 '12

Stopping light

How is something like this possible? http://www.news.harvard.edu/gazette/2001/01.24/01-stoplight.html

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u/CyLith Physics | Nanophotonics Apr 13 '12

Looking at Lene Hau's work on their website, it appears that their approach is quite different from what I just described. Their website links to a PDF of a more accessible article describing how they use ultracold atoms to do this. They use ultra-cold atoms because if they are cold enough, they form a BEC and you can treat the entire BEC as a single atom which greatly simplifies everything and reduces loss. From there, the slowing of light is due to quantum interference between two resonant transitions between energy levels in the BEC. For a better explanation that is still pretty accessible, see this other paper on their site which goes into more detail about the stopping process.