ОЦЕНКА ВЛИЯНИЯ ФУНКЦИОНАЛЬНЫХ ЭЛЕМЕНТОВ НА ПАРАМЕТРЫ СИСТЕМЫ КВАНТОВОГО РАСПРЕДЕЛЕНИЯ КЛЮЧА НА ОСНОВЕ ПРОТОКОЛА B92

Abstract

The influence of the parameters of functional elements on the energy, time and probabilisticcharacteristics of the quantum key distribution system (QKD) based on the B92 protocol is studied.The dependences of the probability of writing correct and erroneous bits into a raw quantumkey sequence are plotted for various lengths of a fiber-optic communication line (FOCL) and theuse of various lasers (EML-laser; DFB-laser; VCSEL-laser and FP-laser) and photodetectormodules (id201; id210; id220; id230). Thus, changes in the probability of writing a correct bit intoa raw quantum key sequence are much more significant than changes in the probability of writingan erroneous bit (50.9 times versus 3.3 times with FWHM=80 pm and a change in the length ofthe FOCL from 10 to 100 km). This is due to the fact that with an increase in the length of theFOCL, the probability of the absence of registration at the receiving station of photons or darkcurrent pulses (DCP) sharply increases. Numerical material indicates a direct proportional dependenceof the probability of writing an erroneous bit on the frequency of generation of noisepulses of single-photon avalanche photodiodes (SAPD). So, with an increase in the frequency ofoccurrence of DCP by 60 times (from 100 to 6000 Hz), the probability of recording an erroneousbit also increases by 60 times (for example, with a FOCL length of 100 km – 6.39 versus 383.3).It has been established that the root-mean-square deviation of the photon delay time is directly proportional to the length of the FOCL and the width of the laser spectrum. With a spectrum widthof FWHM=10 pm and an increase in the FOCL length from 10 to 100 km (by a factor of 10), thestandard deviation of the photon delay time also increases by a factor of 10 (from 4.16 to 41.6 ps).To achieve the best performance of the QKD system as a whole, it is advisable to use a laser witha minimum width of the radiation spectrum, for example, an EML-laser. However, EML-lasers areconsidered the most complex and expensive of all the considered types of lasers, so the use ofEML-lasers significantly increases the cost of the entire QKD system.