“A quantum network uses specially polarized photons to encode an encryption key—a very long series of numbers and letters that can unlock a digital file. The photons are then sent down a fiber optic cable until they reach their destination, a photon detector, which counts them, and delivers the key to the intended recipient. If the photons are interfered with, the individual packets of information are forever altered and the recipient can see the telltale signs of tampering. The next step toward mainstreaming quantum crypto is increasing the distance that photons can travel before they degrade—currently the record is 200 km (124 miles) using a dedicated fiber optic cable.”
