Work

Composable continuous-variable multi-user QKD with discrete modulation: theory and implementation

Year: 2026

Type: article

Abstract: Establishing scalable, secure quantum networks requires advancing beyond conventional point-to-point quantum key distribution (QKD) protocols toward point-to-multipoint QKD protocols. Here, we generalize a well-established discrete-modulated continuous-variable (CV) QKD protocol from the point-to-point to the point-to-multipoint setting. We present a comprehensive security analysis across different scenarios and derive secret key rates for loss-only and noisy channels, both in the asymptotic and the composable finite-size regime. Experimentally, we validate the protocol in a passive optical network with 10 km access links, achieving a composable secure key rate of 2.185×10 −3 bits per symbol (0.273 Mbit/s) against independent and identically distributed collective attacks. Our results demonstrate that discrete-modulated CV-QKD can support access networks with multiple users while relying solely on cost-efficient, off-the-shelf telecommunication components, paving the way toward practical, scalable, and secure quantum networks.

Source: Optica

DOI: 10.1364/optica.588301

Authors: Florian Kanitschar, Adnan A. E. Hajomer, Michael Hentschel, Tobias Gehring, Christoph Pacher

Institutions: AIT Austrian Institute of Technology GmbH, TU Wien, Technical University of Denmark

Language: English

Topic: Quantum Information and Cryptography

Subfield: Artificial Intelligence

Field: Computer Science

Domain: Physical Sciences

Open Access status: gold

Estimated APC paid: $3,208

Funders: Innovationsfonden, European Commission, Österreichische Forschungsförderungsgesellschaft, QuantERA