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Experimental demonstration of finite-size general security via discrete-modulated CVQKD with real time postprocessing

Sven Bodenstedt, Carlos Pascual-García, Nil Canta i Pujol, Martí Sales-Moragues, Mariana Navarro, Pau Gómez Kabelka, Sebastián Etcheverry, Saeed Ghasemi

quant-pharXiv:2609.20596

Abstract

Continuous-variable quantum key distribution (CVQKD) is compatible with telecommunication infrastructure, but implementing composable security with experimentally practical resources has remained challenging, particularly for discrete-modulated (DM) protocols. We report the first experimental demonstration of a DM CVQKD system that generates composable secret keys against general attacks with finite-size block lengths on the order of 106 rounds via a quadrature phase shift keying (QPSK) system. Our implementation follows a variable-length, general security framework enabled by modern entropy accumulation techniques and conic optimization, whose experimental pipeline allows real-time operation on near-commercial hardware.

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