Researchers Use 'Quantum Data Locking' To Create World's First Quantum Enigma Machine

In 2013, Seth Lloyd, a professor of quantum information at Massachusetts Institute of Technology, put forward the idea of creating a "quantum enigma machine" -- one that would be modeled after the World War II-era cipher machines but would use quantum states of photons to encode and encrypt messages. Now, a team of researchers -- led by Daniel Lum, a graduate student at the University of Rochester, and John Howell, a professor of physics at the university -- have taken a step toward realizing this vision by actually demonstrating that an unbreakable encrypted message can be sent with a key that's far shorter than the message. This experiment, described in a new study published in the journal Physical Review A, violates what has hitherto been considered a fundamental rule of cryptography -- that a randomly generated key being used to encrypt a message needs to be at least as long as the message itself. It does so through a technique the researchers call "quantum data locking." The quantum enigma machine developed by the researchers consists of three parts -- a machine that generates photons, a spatial light modulator (SLM) that alters the amplitude and tilt of individual photons and also scrambles its wavefront, and an 8 by 8 photon detecting nanowire array.