Observable-Level Framework for Finite-Key Security in Coherent-One-Way Quantum Key Distribution
Abstract
Practical security analysis of Coherent-One-Way (COW) quantum key distribution requires optical-device modeling, finite experimental statistics, and security inference to be treated consistently without conflating assumptions. We present a modular observable-level simulation framework organized through the pipeline θ_phys -> p -> O -> S_j(O), in which physical source, channel, receiver, and detector parameters determine detector-resolved event probabilities, a finite-block layer applies an effective dead-time treatment and generates aggregate detector counts, and interchangeable security evaluators act on the same observable record. The framework is verified against analytical optical, virtual-state, and finite-key relations and evaluated against reported experimental COW-QKD operating points. The Kato finite-key calculation reproduces the refined experimentally reported secure-key rates most closely at intermediate distances, with deviations of -1.5% at 50 km and -10.3% at 75 km. Monitoring bright-port decoy counts agree within 0.9-2.4%, while remaining distance-dependent dark-port residual identifies the principal model-sensitive observable of the present physical description. Applying Kato and Azuma-Hoeffding concentration treatments to identical detector records isolates the effect of finite-key statistical inference and shows substantially tighter Kato phase-error bounds for rare-event monitoring records studied here. Holding the Kato evaluator fixed, joint optimization of coherent-state mean photon number mu and receiver splitting fraction t_B increases model-predicted secure-key rate by 7.4-20.2% relative to optimization of mu alone with t_B = 0.3. The framework therefore provides a common computational interface for experimental reproduction, controlled security-model comparison, model-based protocol optimization, and modular adversarial stress testing in COW-QKD.
Related
- Security framework for practical quantum key distribution with imperfect devices
- Security of quantum key distribution with passive basis choice and detection-efficiency mismatch for a realistic satellite setup
- Numerical security analysis for practical quantum key distribution
- FVQKD: A Formal Verification of Quantum Key Distribution Security in Rocq
- Fully integrated continuous-variable quantum key distribution with composable security over 100 km
BibTeX
@misc{kuntal2026observablelevel,
title = {{Observable-Level Framework for Finite-Key Security in Coherent-One-Way Quantum Key Distribution}},
author = {Aryan Kuntal and Utkarsh Giradkar and Mudit Chaudhary and Amit D. Lad},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.28239},
eprint = {2610.28239},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.28239},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Observable-Level Framework for Finite-Key Security in Coherent-One-Way Quantum Key Distribution
AU - Aryan Kuntal
AU - Utkarsh Giradkar
AU - Mudit Chaudhary
AU - Amit D. Lad
PY - 2026
DA - 2026/10/20
PB - arXiv
DO - 10.48550/arxiv.2610.28239
UR - https://arxiv.org/abs/2610.28239
AB - Practical security analysis of Coherent-One-Way (COW) quantum key distribution requires optical-device modeling, finite experimental statistics, and security inference to be treated consistently without conflating assumptions. We present a modular observable-level simulation framework organized through the pipeline θ_phys -> p -> O -> S_j(O), in which physical source, channel, receiver, and detector parameters determine detector-resolved event probabilities, a finite-block layer applies an effective dead-time treatment and generates aggregate detector counts, and interchangeable security evaluators act on the same observable record. The framework is verified against analytical optical, virtual-state, and finite-key relations and evaluated against reported experimental COW-QKD operating points. The Kato finite-key calculation reproduces the refined experimentally reported secure-key rates most closely at intermediate distances, with deviations of -1.5% at 50 km and -10.3% at 75 km. Monitoring bright-port decoy counts agree within 0.9-2.4%, while remaining distance-dependent dark-port residual identifies the principal model-sensitive observable of the present physical description. Applying Kato and Azuma-Hoeffding concentration treatments to identical detector records isolates the effect of finite-key statistical inference and shows substantially tighter Kato phase-error bounds for rare-event monitoring records studied here. Holding the Kato evaluator fixed, joint optimization of coherent-state mean photon number mu and receiver splitting fraction t_B increases model-predicted secure-key rate by 7.4-20.2% relative to optimization of mu alone with t_B = 0.3. The framework therefore provides a common computational interface for experimental reproduction, controlled security-model comparison, model-based protocol optimization, and modular adversarial stress testing in COW-QKD.
ER -