Security analyses in quantum key distribution (QKD) and other adversarial quantum tasks often assume perfect device models. However, real-world implementations often deviate from these models. Thus, it is important to develop security proofs that account for such deviations from ideality. In this work, we extend the idea of squashing maps to develop a general framework for analysing imperfect threshold detectors, treating uncharacterised device parameters such as dark counts and detection efficiencies as adversarially controlled within some ranges. This approach enables a rigorous worst-case analysis with exactly characterised devices, ensuring security proofs remain valid under realistic conditions. Our results strengthen the connection between theoretical security and practical implementations by introducing a flexible framework for integrating detector imperfections into adversarial quantum protocols.
@article{arxiv.2503.06328,
title = {Imperfect detectors for adversarial tasks with applications to quantum key distribution},
author = {Shlok Nahar and Devashish Tupkary and Norbert Lütkenhaus},
journal= {arXiv preprint arXiv:2503.06328},
year = {2026}
}
Comments
Fleshed out application to QKD section, including adding comparison with earlier work, adding application to active basis-choice BB84, providing plots for application with the postselection technique, and added reference to "A proof-technique-independent framework for detector imperfections in QKD" which uses these techniques to address correlated imperfections