Performance Analysis of Multiparty GHZ-State Quantum Conference Key Agreement over Optical Fiber Channel
Abstract
Quantum conference key agreement (QCKA) enables multiple spatially separated users to establish a common key with composable information-theoretic security by exploiting multipartite quantum correlations. Greenberger--Horne--Zeilinger (GHZ) states are a natural resource for this task, but their distribution over optical fiber is degraded by transmission loss, polarization decoherence, and detector imperfections. We investigate the finite-key performance of an N-party GHZ-based QCKA system using the N-BB84 protocol, where each optical link is modeled by extending the bipartite erasure--Pauli channel to incorporate detector dark counts. We characterize the impact of this quantum channel on the shared GHZ state and derive closed-form expressions for the error rates. The analytical results reveal that the local bit-error rate depends only on transmissivity and dark counts, while the global phase-error rate compounds over all N−1 links and therefore degrades faster with both distance and the number of parties. These error rates are integrated into a finite-key secret-key-rate (SKR) framework, in which we optimize the parameter-estimation probability via Brent's derivative-free method. Numerical results show that increasing fiber distance and network size reduce the achievable SKR. Furthermore, the optimized parameter-estimation probability consistently increases the SKR and extends the maximum secure distance relative to a fixed-allocation baseline, with comparison to the asymptotic limit quantifying the residual finite-key penalty.
Related
- Enhancing noise robustness in device-independent conference key agreement with asymmetric parity-CHSH inequalities
- Pauli Error Composition Determines the Multipartite Advantage in Conference Key Agreement
- Device-independent conference key agreement from two-body correlators with balanced Dicke states
- Improving the Loss Tolerance of Heralded Photonic GHZ States for Long-Distance Device-Independent Conference Key Agreement
- Beyond Maximal Entanglement: Exact Resources for Multiparty Encrypted Quantum Cloning
BibTeX
@misc{bera2026performance,
title = {{Performance Analysis of Multiparty GHZ-State Quantum Conference Key Agreement over Optical Fiber Channel}},
author = {Dipanjan Bera and Ramniwas Meena and Neel Kanth Kundu},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.05448},
eprint = {2610.05448},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.05448},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Performance Analysis of Multiparty GHZ-State Quantum Conference Key Agreement over Optical Fiber Channel
AU - Dipanjan Bera
AU - Ramniwas Meena
AU - Neel Kanth Kundu
PY - 2026
DA - 2026/10/04
PB - arXiv
DO - 10.48550/arxiv.2610.05448
UR - https://arxiv.org/abs/2610.05448
AB - Quantum conference key agreement (QCKA) enables multiple spatially separated users to establish a common key with composable information-theoretic security by exploiting multipartite quantum correlations. Greenberger--Horne--Zeilinger (GHZ) states are a natural resource for this task, but their distribution over optical fiber is degraded by transmission loss, polarization decoherence, and detector imperfections. We investigate the finite-key performance of an N-party GHZ-based QCKA system using the N-BB84 protocol, where each optical link is modeled by extending the bipartite erasure--Pauli channel to incorporate detector dark counts. We characterize the impact of this quantum channel on the shared GHZ state and derive closed-form expressions for the error rates. The analytical results reveal that the local bit-error rate depends only on transmissivity and dark counts, while the global phase-error rate compounds over all N−1 links and therefore degrades faster with both distance and the number of parties. These error rates are integrated into a finite-key secret-key-rate (SKR) framework, in which we optimize the parameter-estimation probability via Brent's derivative-free method. Numerical results show that increasing fiber distance and network size reduce the achievable SKR. Furthermore, the optimized parameter-estimation probability consistently increases the SKR and extends the maximum secure distance relative to a fixed-allocation baseline, with comparison to the asymptotic limit quantifying the residual finite-key penalty.
ER -