In theory, quantum cryptography (mentioned before is as good as a one time pad, without the need for a secure channel through which to exchange keys. Potentially, it could also employ quantum phenomena to verify that nobody is eavesdropping.
In practice – as with all cryptographic systems – there are weaknesses to be exploited. One known attack exploits a weakness in some sorts of photon detector. Another works by manipulating synchronization signals.
Quantum cryptography may well have some useful applications, but people who expect it to be foolproof and completely secure probably aren’t thinking too well.