Quantum Telecloning Demonstrated?

An anonymous reader writes "According to Physorg eavesdropping on a quantum encrypted link can now be done without detection. From the article: 'The scientists have succeeded in making the first remote copies of beams of laser light, by combining quantum cloning with quantum teleportation into a single experimental step. Telecloning is more efficient than any combination of teleportation and local cloning because it relies on a new form of quantum entanglement - multipartite entanglement.' There is also a PDF of a related paper available here for background material."

Comments

It is not "encryption", it is "modulation"!

[gweihir]

Encryption is a mathematical transformation. Quantym "encryption" has no mathematical transformation in it, it is just a way of modulating signals, i.e. a physical process! That is called "modulation" and has no security properties besides the physical signal properties. No mathematical proofs about this security can be given, since we still do not unterstand the physical universe completely!

Since all previous claims of security rested on not yet well understood physical principles, I am not surprised that once again claims of perfectness by ethically challenged researchers and businesspeople have turned out to be wrong.

Re:It is not "encryption", it is "modulation"!

[jfredett]

Beng somewhat of a mathematician and crypto-buff, let me say this.

Firstly, it IS encryption, there is data being hidden in a non-obvious format,

Dictionary.com says this about the term "Encrypt"

encrypt
tr.v. encrypted, encrypting, encrypts

      1. To put into code or cipher.
      2. Computer Science. To alter (a file, for example) using a secret code so as to be unintelligible to unauthorized parties.

I see nothing about mathematical transforms there. In fact, many ciphers are not mathematical at all, some are completely visual, take for instance Transpostition ciphers, like the hedgerow cipher, (every other letter is taken out and shifted to the end). There is no mathematical transform that you use, no numbers are assigned. Now, notably, you can describe THIS cipher using group theory (it a morphism on a group), however, It can be done with no knowledge of any math at all.

Second, Slightly less of this topic, this is terribly intresting, as the quantum encryption scheme was touted as "completely" unbreakable. And now its been cracked before its even been used. I wonder if anyone will come up with something stronger before (if they ever get to the point where they are usable) Quantum computers invalidate RSA and other factorization based ciphers...

Any other articles out there about different types of quantum encryption?

Heisenberg Uncertainty Principal?

[icleprechauns]

What ramifications does this have on the heisenberg uncertainty principal? I may be no expert, but doesn't this mean that you could make a remote copy of a particle, and measure one's momentum and the other's position with great accuracy?

Hmm, how seredipitous...

[kopasa]

It's interesting that we were just talking about this very article (well the actual release, not this article about it) in a analytical mechanics class I'm taking. One of the things that wasn't mentioned in this article was the fact that the beam of light cloned was only done so to about 66% accuracy. I'm sort of kept from going into more details about this by my own fairly limited grasp on the matrix mechanics, but as the clone wasn't perfect, the uncertainty principle was upheld. It is fairly worrisome to see this study spun much out of proportion though. The opening blurb about Captain Kirk only reinforces untrue stereotypes about the potential of quantum teleportation. Alas, if journalists were physicists...

Re:What it all really means

[Loconut1389]

I'll feed the troll..

Feasibly, someone that had access to the cables could cut them, put a receiver, a transmitter, and a computer that receives, records and retransmits everything in and splice everything up properly when done- aside from a temporary and puzzling outage- no one would be the wiser.

It can be determined from reflectometry exactly where the break is, and someone would go out and check the cable eventually with an ROV or something and find the splice, but I'd imagine for a while you could have a tap in place as long as the interruption was minimal.

Around here, when there's a fiber cut, it takes hours- but I assume some of that is discovering the cut, finding a crew and getting to the site. I would suppose if you put one of the worlds top splicers right there that the interruption could be made fast enough that the techs monitoring the connection would be confused but would chalk it up to some sort of temporary bend or other error.

I am not a fiber tech, but all of that seems fairly reasonable to me.

In other words, I don't think quantum teleportation is necessary or even applicable to straight forward fiber implementations that don't depend on the orientation of photons.