FAU LMQ Talk: Finite-Size Security Proof for DM CV-QKD Protocols

Title: Finite-Size Security Proof for DM CV-QKD Protocols

Speaker: Florian Kanitschar

Affiliation: Austrian Institute of Technology (AIT) and Technische Universität Wien

Abstract:

Discrete-Modulated (DM) Continuous-Variable Quantum Key Distribution (CV-QKD) protocols are strong candidates for commercial quantum communication networks, offering experimental simplicity and practical feasibility. While tight security proofs exist for the asymptotic regime, extending these analyses to the finite-size regime remains an active field of research, mainly due to the inherent infinite-dimensional nature of CV protocols.

This talk provides a composable finite-size security proof for a general DM CV-QKD protocol, addressing independently and identically distributed (i.i.d.) collective attacks. After a brief historical overview, we present a novel energy testing theorem to bound the effective dimension of Bob's quantum system, ensuring rigorous security within Renner’s epsilon-security framework. Another key ingredient is the use of acceptance testing, which we argue is the appropriate statistical tool for finite-size security analyses, replacing the parameter estimation methods typically employed in asymptotic proofs. Additionally, we extend and apply a numerical security proof technique to compute tight lower bounds on the secure key rate.

To illustrate the practical relevance of our method, we demonstrate its application to a quadrature phase-shift keying protocol. We evaluate the protocol's performance under various conditions, including untrusted ideal detectors and trusted non-ideal detectors, showcasing its robustness and adaptability to realistic experimental setups.

Underlying paper: Finite-Size Security for Discrete-Modulated Continuous-Variable Quantum Key Distribution Protocols; F. Kanitschar, I. George, J. Lin, T. Upadhyaya, and N. Lütkenhaus, PRX Quantum 4, 040306 (2023)