"Quantum key distribution (QKD) can already keep secret the key to a code. "I was trying to think of alternatives," says Seth Lloyd at the Massachusetts Institute of Technology. "It occurred to me that it would be interesting to quantise the Enigma machine."

Vadim Makarov, who runs a quantum hacking lab at the University of Waterloo, Canada, says quantum Enigma is more difficult to implement than QKD but has other benefits. QKD uses quantum mechanics to create the key, requiring back-and-forth communication, but in quantum Enigma, the key is pre-arranged, so the only transmissions are the messages themselves."
http://www.newscientist.com/article/dn23837-quantum-version-of-nazi-enigma-machine-is-uncrackable.html#.UgEgd-Wwek_