Noise provides means to crack quantum encryption

Nature : In theory, sending quantum-encrypted messages is secure because any attempt at snooping is apparent to the recipient. In practice, the physical systems that encrypt the messages are imperfect. Noise creeps in. Still, until now, physicists had believed that if noise remained below 20%, snooping would be exposed. The University of Toronto’s Feihu Xu, Bing Qi, and Hoi-Kwong Lo have devised a method to intercept quantum encrypted communication while remaining below the 20% detection threshold.