Towards a point-to-point CV-QKD system: Implementation challenges and perspectives

TL;DR

This paper analyzes the practical challenges and implementation strategies for deploying a point-to-point CV-QKD system over optical fiber, focusing on hardware, signal processing, and future deployment perspectives.

Contribution

It provides a comprehensive overview of the design, hardware architecture, and processing techniques for CV-QKD systems, and outlines a roadmap for deployment in Brazil.

Findings

Identification of key impairments affecting CV-QKD performance

Development of digital signal processing techniques for noise mitigation

Proposal of hardware architectures and software frameworks for implementation

Abstract

This article presents an analysis of the practical challenges and implementation perspectives of point-to-point continuous-variable quantum key distribution (CV-QKD) systems over optical fiber. The study addresses the physical layer, including the design of transmitters, quantum channels, and receivers, with emphasis on impairments such as attenuation, chromatic dispersion, polarization fluctuations, and coexistence with classical channels. We further examine the role of digital signal processing (DSP) as the bridge between quantum state transmission and classical post-processing, highlighting its impact on excess noise mitigation, covariance matrix estimation, and reconciliation efficiency. The post-processing pipeline is detailed with a focus on parameter estimation in the finite-size regime, information reconciliation using LDPC-based codes optimized for low-SNR conditions, and privacy amplification employing large-block universal hashing. From a hardware perspective, we discuss modular digital architectures that integrate dedicated accelerators with programmable processors, supported by a reference software framework (CV-QKD-ModSim) for algorithm validation and hardware co-design. Finally, we outline perspectives for the deployment of CV-QKD in Brazil, starting from metropolitan testbeds and extending toward hybrid fiber/FSO and space-based infrastructures. The work establishes the foundations for the first point-to-point CV-QKD system in Brazil, while providing a roadmap for scalable and interoperable quantum communication networks.