Modulation leakage-free continuous-variable quantum key distribution

TL;DR

This paper introduces a modulation leakage-free continuous-variable quantum key distribution system that enhances security by eliminating a known side-channel vulnerability, using standard telecommunication technology and digital signal processing.

Contribution

The work presents a practical CVQKD implementation that removes modulation leakage vulnerabilities, ensuring security against collective attacks without sacrificing performance.

Findings

Successfully demonstrated a leakage-free CVQKD system

Generated a composable secret key secure against collective attacks

Achieved practical implementation with standard telecommunication components

Abstract

Distributing cryptographic keys over public channels in a way that can provide information-theoretic security is the holy grail for secure communication. This can be achieved by exploiting quantum mechanical principles in so-called quantum key distribution (QKD). Continuous-variable (CV) QKD based on coherent states, in particular, is an attractive scheme for secure communication since it requires only standard telecommunication technology that can operate at room temperature. However, a recently discovered side-channel created in the process of state preparation leads to a leakage of information about the transmitted quantum state, opening a security loophole for eavesdroppers to compromise the security of the CVQKD system. Here, we present a CVQKD system without this modulation leakage vulnerability. Our implementation is based on a baseband modulation approach, and uses an in-phase and quadrature (IQ) modulator for state preparation and radio frequency heterodyne detection together with carefully designed digital signal processing for state measurement. We consider practical aspects in the implementation and demonstrate the generation of a composable secret key secure against collective attacks. This work is a step towards protecting CVQKD systems against practical imperfections of physical devices and operational limitations without performance degradation.