A Quantum Enigma Machine: Experimentally Demonstrating Quantum Data   Locking
  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 a shorter key and still provide information-theoretic security. We present one of the first feasible experimental demonstrations 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. 
Daniel J. Lum, M. S. Allman, Thomas Gerrits, Cosmo Lupo, Varun B.   Verma, Seth Lloyd, Sae Woo Nam and John C. Howell
quant-ph physics.optics