Quantum Byzantine Agreement Protocol Under Noisy Conditions
Evaluating the Impact of Qubit Decoherence on the Protocol’s Success Rate
P.M. Meswani (TU Delft - Electrical Engineering, Mathematics and Computer Science)
T.J. Coopmans – Mentor (TU Delft - QCD/Coopmans Group)
Arie Van Deursen – Graduation committee member (TU Delft - Software Engineering)
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Abstract
Byzantine agreement protocols allow distributed systems to achieve consensus despite faulty nodes. The classical solution to the Byzantine agreement can only tolerate less than 1/3 of the total nodes being faulty, while a quantum-aided protocol has the potential to tolerate up to 1/2 of the nodes being faulty. However, the quantum states used in the protocol are vulnerable to decoherence, a process that results in the degradation of a quantum state. This research investigates how memory decoherence affects the failure rate of a three-party quantum Byzantine agreement protocol. The primary contribution is demonstrating that the protocol is resilient to carbon T2 decoherence, as its Z-basis measurement scheme is insensitive to phase errors. Conversely, the failure probability increases with decreasing carbon T1 decoherence values. Extrapolating from the observed trend of decreasing failure with longer T1 coherence times, the protocol’s performance on nitrogen vacancy center hardware is expected to approach the ideal, noiseless limit due to their experimentally established long T1 times.