
Photons pair up like superconducting electrons - jonbaer
http://www.nature.com/news/photons-pair-up-like-superconducting-electrons-1.22868
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Filligree
Electrons interact with each other. Photons _don 't_, unless you get to
extremely high energies.

We'll see, I suppose.

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splittingTimes
> Electrons interact with each other.

In principle correct, but in the particular case of Cooper pairs (responsible
for the super conduction) the el-el interaction plays a subordinate role.
Actually, the Coulomb force is counter-productive to building electron pairs,
as electrons repel each other.

The effectively attractive el-el coupling of Cooper pairs is mediated by the
electron-phonon interaction (Phonons are the quantized lattice vibrations).

The following picture might help:

When a negatively charged electron moves through the lattice, the positive
cores of the lattice ions are attracted and move away from their equilibrium
position. This causes a lattice polarization. In metals, the ion movement is
much, much slower then that of the electrons. So when the polarization-
inducing electron has already moved on, the lattice is still out of its
equilibrium position. A second electron that comes into that region, "sees"
the lattice polarization and the elongated positive ions and is attracted to
it.

Thus the lattice vibration has mediated an effectively attractive coupling
between the two electrons.

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AnimalMuppet
And, to more directly address filigree's point: The claim is that photons can
(indirectly) interact via the same mechanism, because both photons can
interact with the atoms they are passing through.

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deepnotderp
Wow, this is certainly surprising. I wonder if there are any useful
applications?

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Koshkin
Well, the interesting part of the electron-electron pairing is that two
fermions form a boson, which is what accounts for superconductivity. In the
case of paring of photons, which are bosons to begin with, the effect is more
subtle; I can only hope that it will eventually find a useful application,
e.g. in communications or quantum computing...

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deepnotderp
Yeah, I found that weird too, but apparently the paper says that this is
mathematically equivalent if they also use virtual phonons, which is
interesting indeed. I wonder if these are collective excitations (the boson
equivalent of quasiparticles) instead of something similar to Cooper pairing.
I haven't read the paper though, so this is just me thinking out loud.

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JackFr
Looks like we can throw all the existing invisibility cloak research out the
window.

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deepnotderp
Why?? I see no reason that this should influence metamaterials research. After
all, they report this effect to only manifest itself in water and a couple
other transparent liquids.

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JackFr
I was kidding. Clearly I'm not up to speed on latest invisibility research.

