Photon counter extends quantum communication systems

Gregory S. Kanter

Kouichi Yamazaki, Osamu Hirota, Masao Nakagawa

A. M. Timofeev

An asynchronous quantum-cryptographic communication channel with a receiving module based on a photon counter with a dead time of an extending type was investigated. An expression for estimating the ratio of the probability of erasing binary symbols "0" P(–/0) to the probability of these symbols being erroneous Perr0 has been obtained. Based on the results of mathematical modeling, the dependences of the ratio P(–/0) / Perr0 on the average count rate of signal pulses at the output of the photon counter during the transmission of symbols “0” ns0 for various average duration of dead time of the extended type τd were established. The performed studies have shown that with an increase in ns0, these dependences at first practically do not change and have values close to unity, but then they drop down to the lowest values and go into saturation. This takes place both in the absence of a dead time of the prolonging type, and in its presence.

A. M. Timofeev

Expressions are determined to estimate the probabilities of erroneous recording of binary data of a quantum-cryptographic communication channel containing a photon counter with an extending dead time.According to the results of mathematical modeling, the dependences of the probabilities of erroneous data recording at the output of the communication channel are established on the average single-photon transmission time of the characters "0" and "1", on the basis of which the choice of the smallest average transmission time per bit (character), providing the smallest loss of information transmitted, is justified.

Harald Weinfurter

Anton Zeilinger