
The information capacity of a single photon (2012) - adamnemecek
https://arxiv.org/abs/1211.1427
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dahart
Tl;dr by using the photon's color (wavelength), we get more bandwidth than the
current qubit encoding, which is based on polarization.

This would be loosely similar to using multiple voltage levels to build
trinary, quaternary, etc. digital circuits or CPUs. (Which has been done in
the past and some people still speculate will come back into fashion.)

It's also somewhat similar to the idea of FM radio, where the signal is
encoded in the frequency differences.

It looks like they dropped the polarization encoding to use wavelength only.
If I'm reading it right, then I'd guess there an extra easy +1 bit (at least)
by using both wavelength and polarization.

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brianpgordon
The answer from the paper:

Theoretically infinite, but in their more realistic model they came up with 5
bits.

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irrational
The gap between 5 and infinite bits seems a bit on the large side.

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lisper
In theory there is no difference between theory and practice but in practice
there is.

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nabla9
Arbitrarily tunable orbital angular momentum of photons (2016)
[https://www.nature.com/articles/srep29212](https://www.nature.com/articles/srep29212)

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platz
If the holographic principle is true there are a lot less degrees of freedom
than would otherwise seem available

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Dylan16807
You have to hit black-hole-level information densities for it to matter, don't
you?

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platz
yes, but that entails an upper-bound... finite.

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Dylan16807
When it comes to a single particle, I wouldn't have thought an infinite number
of degrees of freedom "seem available" in the first place.

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platz
That is exactly what the article posits as a hypothesis.

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Dylan16807
Maybe? I would have said they're using _one_ degree of freedom, the frequency.

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platz
As far as our model is concerned it's a distiction without a difference
because were talking about all the bits of entropy, i.e. the information. If
it's a represtanble state, it counts as a bit of information.

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coderpact
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