内容：

Claude Shannon proved in 1949 that information-theoretic-secure encryption is possible if the encryption key

is used only once, is random, and is at least as long as the message itself. Notwithstanding, when information is

encoded in a quantum system, the phenomenon of quantum data locking allows one to encrypt a message with

an exponentially shorter key and still provide information-theoretic security. We present the first feasible experimental

demonstration of quantum data locking for direct communication and propose a scheme for a quantum

enigma machine that encrypts 6 bits per photon (containing messages, new encryption keys, and forward error

correction bits) with less than 6 bits per photon of encryption key while remaining information-theoretically

secure.