Photon statistics determination for single photon based quantum key distribution

In practice the most advanced field of quantum information science is quantum cryptography. The best known example of quantum cryptography is quantum key distribution (QKD) which offers an information-theoretically secure solution to the key exchange problem. There are QKD protocols which rely on a quantum channel that is able to transmit single photons. This can be implemented by using very low-power coherent light field, where values of bits are encoded into the polarization state of photons. Therefore, it is important to know the photon number distribution of the light source. In this paper we present the reconstruction of photon statistics for different pulsed light sources radiating at 850 nm (a common choice for free space quantum communication), using only a single on-off photon counting detector.