[Senator Bedfellow]

The NSA can spend a gigantic amount of money on something they consider to be important, and quantum computation cuts to the very core of its mission. It could lay the world's secrets absolutely bare.

Until we have feasible quantum cryptography systems, which may well arrive even before large-scale quantum computing ;)

[Physicist]

Been there, done that. The claim is that the U.S. government does use quantum cryptography in specific circumstances. It's dreadfully inconvenient and inefficient, though, so it will probably never have widespread use among our enemies. The problem is that unlike any trapdoor cipher, which can be applied at any layer, quantum cryptography can only be applied at the physical layer. It's as feasible as it can get, but it can't be made portable, and it can't use public bands or cables.