Resource Analysis for Quantum-Aided Byzantine Agreement with the Four-Qubit Singlet State

In distributed computing, a Byzantine fault is a condition where a componentbehaves inconsistently, showing different symptoms to different components ofthe system. Consensus among the correct components can be reached byappropriately crafted communication protocols even in the presence of byzantinefaults. Quantum-aided protocols built upon distributed entangled quantum statesare worth considering, as they are more resilient than traditional ones. Basedon earlier ideas, here we establish a parameter-dependent family ofquantum-aided weak broadcast protocols. We compute upper bounds on the failureprobability of the protocol, and define and illustrate a procedure thatminimizes the quantum resource requirements. Following earlier workdemonstrating the suitability of noisy intermediate scale quantum (NISQ)devices for the study of quantum networks, we experimentally create ourresource quantum state on publicly available quantum computers. Our workhighlights important engineering aspects of the future deployment of quantumcommunication protocols with multi-qubit entangled states.