Practical Quantum Cryptosystem for Metro Area Applications

A practical quantum cryptosystem prototype has been developed for metro area applications. It is of the size of a desktop and incorporates a temperature-independent optical interferometer, a highly reliable photon detector module, and random number generators. It supports various functions, including bit/frame synchronization, BB84 bit reconciliation, error correction and privacy amplification for quantum key generation, and encrypted communication. Two weeks of testing using a commercial fiber in the field demonstrated its ability to continuously generate final keys and to perform crypto communication using the keys.