Noisy Byzantine Agreement in Quantum Networks
Impact of Gate Errors on a Weak Broadcast Protocol
Alexandru Cirjaliu - Davidescu (TU Delft - Electrical Engineering, Mathematics and Computer Science)
T.J. Coopmans – Mentor (TU Delft - QCD/Coopmans Group)
A. van Deursen – Graduation committee member (TU Delft - Electrical Engineering, Mathematics and Computer Science)
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Abstract
The Weak Broadcast protocol is a quantum solution to the Byzantine agreement problem. However, its practical applicability remains uncertain due to the impact of noise in quantum systems. Building on prior work by Guba et al., which presented a quantum Byzantine agreement protocol using a four-qubit singlet state, this research investigates how gate-level noise affects the success probability of the protocol, focusing on a Linear Circuit implementation. Gate noise is a critical challenge in quantum hardware, as quantum gates are a primary source of errors in current devices. Using the NetSquid and SquidASM frameworks, the protocol was reproduced and extended with a realistic depolarizing noise model to simulate noisy conditions across different scenarios. Results show that even modest noise levels (0.001% - 0.01%) lead to a sharp rise in failure probability, and at 1% noise, the protocol fails often. These findings highlight the protocol's vulnerability to gate noise and suggest that its practical deployment would require significant error mitigation and fault-tolerant architectures, or a design adapted to better tolerate gate-level noise. This work offers a reproducible simulation framework and provides insights into the protocol's robustness under noisy conditions, addressing a gap in current literature.