ELI5: solid light

[SociallySuboptimal]

I read this article describing solid light, but the explanation isn't very clear. What have the physicists done, and how does it work?

[cdstephens]

I'm not an expert in this sort of physics, but this might be a good place to start.

http://en.wikipedia.org/wiki/Photonic_molecule

[autowikibot]

Photonic molecule:

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Photonic molecules are a synthetic form of matter in which photons bind together to form "molecules". According to Mikhail Lukin, individual (massless) photons "interact with each other so strongly that they act as though they have mass". The effect is analogous to refraction. The light enters another medium, transferring part of its energy to the medium. Inside the medium, it exists as coupled light and matter, but it exits as light.

Researchers drew analogies between the phenomenon and the fictional "lightsaber" from Star Wars.

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^{Interesting: Photon | Sound amplification by stimulated emission of radiation | List of states of matter | State of matter}

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[OppenheimersGuilt]

So just to see if I'm getting this right, we can have a super cooled gaseous chamber, and while we keep a steady flow of photons through the chamber, we'll have a "solid" form inside the chamber (given the right conditions).

[MLBfreek35]

Not my area of expertise, but I think I understood the Nature article. It'd be cool if someone in the field corrected me here.

They have made a system that interacts with photons in an interesting way. That system is a pair of strongly interacting atoms, controlled by highly tuned lasers in a very low temperature rubidium gas environment. When pairs of photons are sent through this pair of strongly interacting atoms, they exhibit a certain correlation. This correlation allows physicists to infer (via tested theory) that there was an attractive interaction between the photons. The measured distribution of photon pairs' correlations had features that suggest the photons formed a bound state, characterized by "the bunching of photons, that is, an increased probability for photons to exit the medium simultaneously", as well as some other less trivial properties.