Building a globe-spanning quantum Internet

The research and development company Battelle is currently building out a nationwide quantum network that would stretch from Boston to Georgia, eventually reaching all the way to California. A similar project is already under way in China, spanning from Shanghai to Beijing.

They're the first networks of their kind, using the essential qualities of light to protect messages in transit. But as the quantum-encrypted networks come to life, they're raising real questions about the future of cryptography. Quantum networks use long encryption keys that are distributed across the network as bursts of light. To establish a key, one party generates random signal and the other listens in: whatever comes out of the network is the new encryption key. But what if someone else is listening in? To protect against interception, the network relies on the observer effect — the principle that light can’t be intercepted without altering the signal itself. For cryptography purposes, that means that if you're using the right protocols, you can ensure no one else is on the line. If everything goes right, it would mean a perfect encryption system, fueled by big, random keys that are impossible to intercept.