Noise-immunity Kazan quantum line at 143 km regular fiber link

Abstract

in the direction of "Photonics and Optoinformatics", candidate of technical sciences, head of lab. at the Kazan Quantum Center of the KNRTU-KAI. Area of interest: quantum communications, optoelectronics, photonics.

Visual media for monitoring trunk quantum networks

“…The average secret key rate (SKR) was 12 bits per second with line losses of 37 dB at a distance of 143 km during a multi-day field test. Earlier in [7], an attempt was made to implement stable commercial long-distance QCs on a regular fiber line, where for conditions similar to our [2,3] conditions (37 dB loss), a ratio of key generation speed to a clock frequency of about 7 bit/s per 100 MHz was obtained, which is about 2 times lower than the values for our test 12 bit/s at 100 MHz in Kazan [2,3]. However, in [7] it was impossible to obtain a sufficiently stable operation of the QC system for several days to be sure of the reliability of the safety parameters.…”

“…In this paper, we studied the trends and correlations of performance parameters for the first in Russia experimental long-distance QC at 143 km at 37 dB losses on standard FOCLs [2,3], which exceeds 100 km (the size of the small standard line FOCLs along railways) with attenuation of more than 25 db.…”

“…In August 2019, we experimentally demonstrated the trunk QC [2,3] at a distance of 143 km between the city of Kazan and the urban-type village of Apastovo in the Republic of Tatarstan using a modified quantum key distribution prototype [4,5] that provides high noise immunity of lines and network nodes due to phase coding in a subcarrier wave [6]. The average secret key rate (SKR) was 12 bits per second with line losses of 37 dB at a distance of 143 km during a multi-day field test.…”

“…During a field test of the trunk QC in Kazan [2,3] in August 2019, a number of QBER values were obtained (values within the acceptable QBER value were taken less than 4 %), which even at the first examination has a trend structure that meets nonrandom factors (temperature, humidity etc). In Fig.…”

Robust diagnostics of dark counts for quantum networks

“…Robust diagnostics of the working complexes of quantum communication (QC) [1] is crucial for the implementation of quantum networks capable of working in both urban [2,3] and trunk [4,5] standard fiber-optic communication lines. At the same time, from the point of view of communication systems, trunk quantum networks (TQN) with lines of more than 100 km and losses between nodes of more than 25 dB, where the signal-tonoise ratio cannot be considered large, are particularly difficult to implement [6].…”