Single photon counting at telecom wavelength and quantum key distribution

A brief overview is given of single photon detector performance requirements for quantum cryptography applications. The analysis is made with respect to restrictions necessary to secure the quantum key distribution channel. InGaAs/InP avalanche photodiode performance is analysed for single photon counting at 1550 nm. Quantum efficiency, dark current and afterpulsing probability (for times up to 100 mus after an initial avalanche) are studied in a wider temperature range than previously reported (0degreesC to -80degreesC). We show that photon counting is a bottle-neck in current quantum key distribution systems and provides the source for future performance improvement.