Polarization shift keying for free space QKD: Effect of noise on reliability of the QKD protocols

A practical scheme for measurement-device-independent polarization shift keying using two state polarization encoding is presented. Most of the previous work on optical free space laser communications through the atmosphere was concentrated on intensity modulated systems. However, polarization modulated systems may be more appropriate for such communication links, because the polarization seems to be the most stable characteristic of a laser beam while propagating through the atmosphere. Thus, a detailed comparison between intensity and polarization modulated systems is of big interest.