Composable Continuous-Variable Multi-User QKD with Discrete Modulation: Theory and Implementation

• URL: http://arxiv.org/abs/2406.14610v2
• Date: Fri, 12 Sep 2025 07:30:00 GMT
• Title: Composable Continuous-Variable Multi-User QKD with Discrete Modulation: Theory and Implementation
• Authors: Florian Kanitschar, Adnan A. E. Hajomer, Michael Hentschel, Tobias Gehring, Christoph Pacher,
• Abstract summary: We generalize a well-established discrete-modulated continuous-variable (CV) QKD protocol from the point-to-point to the point-to-multipoint setting.<n> Experimentally, we validate the protocol in a passive optical network with 10 km access links, achieving a composable secure key rate of $2.185 times 10-3$ bits per symbol.
• Score: 2.7163502859846873
• License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
• 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 four trust scenarios and derive secret key rates for both loss-only and noisy channels, in the asymptotic and composable finite-size regimes. Experimentally, we validate the protocol in a passive optical network with 10 km access links, achieving a composable secure key rate of $2.185 \times 10^{-3}$ 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.

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