# Demonstration of a quantum key distribution network in urban fibre-optic communication lines

## TL;DR

This paper demonstrates a practical quantum key distribution network in urban fibre-optic lines, integrating polarization and phase encoding, enabling secure key renewal in existing encryption systems within seconds.

## Contribution

It presents a real-world implementation of a QKD network using trusted repeaters and dual encoding methods in urban fibre lines, a step forward in practical quantum communication.

## Key findings

- Successful deployment of a QKD network in Moscow's urban fibre infrastructure.
- Integration of polarization and phase encoding techniques.
- Achieved key refresh times of up to 14 seconds for encryption devices.

## Abstract

We report the results of the implementation of a quantum key distribution (QKD) network using standard fibre communication lines in Moscow. The developed QKD network is based on the paradigm of trusted repeaters and allows a common secret key to be generated between users via an intermediate trusted node. The main feature of the network is the integration of the setups using two types of encoding, i.e. polarisation encoding and phase encoding. One of the possible applications of the developed QKD network is the continuous key renewal in existing symmetric encryption devices with a key refresh time of up to 14 s.