
Physicists use photons to carry messages from electrons 1.2 miles apart - jonbaer
http://news.stanford.edu/news/2015/november/cryptography-quantum-tangle-112415.html
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cft
"Quantum supercomputers promise to be exponentially faster and more powerful
than traditional computers, Yu said, and can communicate with immunity to
hacking or spying. "

Either Yu or the author of this write-up is wrong. I suspect the author...

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kristopolous
are you familiar with the potentials of "quantum cryptography"? If not, just
do a web search ... that was the reference here.

I'm not a physicist so I can't speak with any authority on the claims but
Bruce Schneier in Applied Cryptography claimed that a system which used the
principles of quantum cryptography as the transport of the data had already
been developed and deployed at great cost between a few key organizations, and
this was in a 1996 book.

I'll use this as a basis for a [fallacious] appeal to authority argument here
and claim that the "less hackable" claim can't be dismissed outright. But
again, I'm not even going to attempt to make any physics claim here --- I
simply don't have such credentials.

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dogma1138
Those systems afaik currently do not encrypt data but ensure that no one is
tapping into the fiber and retransmitting the signal as they cannot reproduce
the photons in their original quantum state.

It's pretty standard these days for government point to point links that use
existing laid fibers or go through existing metro ducts.

[http://www.lanl.gov/projects/feynman-
center/technologies/inf...](http://www.lanl.gov/projects/feynman-
center/technologies/information-technology-communications/quantum-enabled-
security-qes.php)

~~~
vectorjohn
The quantum part simply allows perfect distribution of keys. So person A can
tell person B what key to use, and person B can know with certainty that
nobody else saw it. Then they just use regular encryption.

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kristopolous
Does asymmetric key exchange handle this problem, or am I missing some attack
vector?

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vectorjohn
Well, I'm not actually sure if there's any problem with asymmetric keys, now.

I think, since asymmetric keys depend on factors of big prime numbers, they
are vulnerable to quantum computers actually. Whenever those start working,
keys become easily breakable.

[https://en.wikipedia.org/wiki/Post-
quantum_cryptography](https://en.wikipedia.org/wiki/Post-quantum_cryptography)

~~~
kristopolous
No it doesn't. It depends on the existence of asymmetric algorithms. There's
as far as I know, a number of classes of algorithms that have a good potential
to satisfy this.

~~~
vectorjohn
That sounds neat, but we're not using any of those. And I don't see a [0] with
a link anywhere in your comment. What I read, cited above, said that all
existing asymmetric key algorithms are easily broken with quantum computers.

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Panoramix
"Photons from two different sources have different characteristics, like color
and wavelength. If they have different wavelengths, they cannot interfere, Yu
said"

Can somebody explain why that is the case?

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Retric
I don't think it's 100% true as stated.
[https://en.m.wikipedia.org/wiki/Photomixing](https://en.m.wikipedia.org/wiki/Photomixing)

~~~
Panoramix
That seems like a simple superposition, while I'm going to assume the author
meant some sort of quantum interference.

~~~
Retric
I thought superposition in like was a QM effect.

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journeeman
Why are photons required to "act as the messengers of an electron's spin"?
Entanglement works without any communication between the entangled particles,
right?

