Phase error estimation for passive detection setups with imperfections and memory effects
Abstract
We develop a generic framework to bound the phase error rate for quantum key distribution protocols using passive detection setups with imperfections and memory effects. This framework can be used in proof techniques based on the entropic uncertainty relation or phase error correction, to prove security in the finite-size regime against coherent attacks. Our framework can incorporate on-the-fly announcements of click/no-click outcomes on Bob's side. In the case of imperfections without memory effects, it can be combined with proofs addressing source imperfections in a modular manner. We apply our framework to compute key rates for the decoy-state BB84 protocol, when the beam splitting ratio, the detection efficiency, and dark counts of the detectors are only known to be within some ranges. We also compute key rates in the presence of memory effects in the detectors. In this case, our results allow for protocols to be run at higher repetition rates, resulting in a significant improvement in the secure key generation rate.
Cite
@article{arxiv.2508.21486,
title = {Phase error estimation for passive detection setups with imperfections and memory effects},
author = {Zhiyao Wang and Devashish Tupkary and Shlok Nahar},
journal= {arXiv preprint arXiv:2508.21486},
year = {2025}
}
Comments
There is a local error in the lambdamin (subspace estimation) computation for BB84 passive protocol. The method used in the old version implies that the security proof, thus (delta,a,q_Z calculation), should be done on some different POVM on Bob's side. For the new version, we improve the lambdamin computation so that the security proof is done on the original POVM