US Patent 7460669 - 2-bit encoding using single photon

http://www.freepatentsonline.com/7460669.html

This patent from Toshiba has a fairly early priority date (Oct. 25, 2000) and seems to present some very basic claims to using a single photon to encode multi-bit data states which may be important to future quantum computing. Claim 1 reads:

1. A method of encoding at least two bits of information on a single photon, the method comprising the step of setting at least two parameters of the photon to respectively correspond to the at least two bits of information such that the at least two bits of information are encoded onto the photon using the at least two parameters.