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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."
Wrong.
All the article claims is that the Evesdropper's location will be undetected. The fact that someone is attempting to eavesdrop will still be detected, and there are several well known proofs of security of this fact.
FTF Press Release
"Quantum cryptographic protocols are so secure that they can not only discover tapping but also where and how much information is leaking out. Now, using telecloning, the identity and location of the eavesdropper can be concealed."
Quantum cryptography is absolutely secure as long as the laws of quantum mechanics are true. And even if the laws of quantum mechanics are false, one can still do secure cryptography from some very weak assumptions (it follows from violating Bell's inequalities and no-signalling) see this
Deconstruct the State
Disclaimer: IAAQIS (I Am A Quantum Information Scientist).
The parent poster (wwwrench) is completely, 100% correct. Is this really Slashdot, or did I type the wrong URL?
Seriously, though, the parent poster is bang-on. To elaborate a bit, quantum cryptography would be more informatively called quantum key distribution (although both names are common in practice). All it does is allow you to distribute a key for a one-time pad in a secure method, given that the laws of quantum mechanics are at least partially correct (one-time pads are information-theoretic secure, provided the key is not compromised or re-used). If somebody tries to eavesdrop, you can detect it, and respond accordingly. That response could be privacy amplification (if the information the eavesdropper gained was only partial), re-trying the protocol, or bombing the eavesdropper to smithereens. That last possibility is why quantum telecloning might be useful.
One other hitch is that quantum key distribution requires a small shared secret in order to authenticate the two parties trying to generate a key. Thus, quantum key distribution is not a complete replacement for public-key cryptography.