US Patent 7460669 Encoding, decoding and communication method and apparatus

An encoding method, decoding method and a communication method using single photons where information is directly encoded into each photon. In one embodiment at least two out of the three parameters of phases, polarization, and energy are used to encode information. In another embodiment, three or more non-orthogonal states with respect to each parameter are used. A further embodiment is also described which uses selective grouping of the results in order to more clearly detect the presence of an eavesdropper. Apparatus capable of performing the methods are also provided.