The central principle of quantum mechanics--that the act of measuring a quantum object actually changes it--has some pretty amazing potential in the world of cryptography. And Los Alamos National Laboratory just revealed that it has been using a new design of quantum cryptography setup for more than two years.
Quantum cryptography isn't new; the potential for completely secure transmission has been enough to attract lots of development efforts from banks and governments. You can even buy a fairly simple system right now. And these are literally completely secure; any attempt to eavesdrop is necessarily obvious, because the mere act of eavesdropping physically changes the transmission. But that means that quantum encryption has, until now, been exclusively a one-to-one connection, as over a single line. Networks haven't been possible.
But Los Alamos has pioneered what they're calling a "quantum internet." I'll let Technology Review explain it: