Future proofing network encryption technology with continuous-variable quantum key distribution

TL;DR

This paper demonstrates the practical implementation of continuous-variable quantum key distribution (CVQKD) in real-world field trials, showing its potential to enhance network security by generating secret keys over existing communication links.

Contribution

It provides the first field trial evidence of CVQKD's feasibility in diverse real-world optical network environments, integrating quantum and classical data channels.

Findings

Achieved secret key rates up to 434.8 kbps under realistic conditions

Successfully multiplexed quantum and classical data over existing fiber infrastructure

Demonstrated CVQKD's robustness in harsh field environments

Abstract

We demonstrate a proof-of-concept establishment of quantum-secure data transfer links in field trials at two locations in Denmark: on the campus of Technical University of Denmark in Lyngby and between power grid nodes owned and operated by Energinet in Odense. Several different links, implemented physically using optical ground wires, underground fibers as well as their combinations, were investigated. Coherent `quantum' states at 1550 nm, prepared and measured using a semi-autonomous continuous-variable quantum key distribution (CVQKD) prototype, were multiplexed in wavelength with `classical' 100Gbps encrypted data traffic from a pair of commercial layer-2 network encryption devices operating at around 1300 nm. Under the assumptions of real-time data processing, we estimate average secret key rates of $434.8, 148.6$, and $78.3$ kbps in the asymptotic limit for diverse channels with losses (at 1550 nm) of 4.1, 5.5, and 6.7 dB, respectively. The demonstrations permit an evaluation of the prototype's tolerance to harsh field conditions and showcase that CVQKD can serve as an additional layer to protect sensitive network traffic propagating on insecure channels.