Unbreakable Encryption

I read this cool article yesterday on 'unbreakable encryption' using data transmitted along an optical fiber. I still don't understand if the the encryption is unbreakable or if the real issue is that undetectable eavesdropping becomes impossible. Apparently the very act of eavesdropping would interfere with the optical beam being transmitted-kind of reminds me of the Heisenberg Uncertainty Prinicple and Observer Effect-where any interference in a quantum system alters its natural state. I just always wonder when someone describes crypto as 'unbreakable'. We humans can be very crafty.