Scalable and Highly Fault-Tolerant Circular Quantum Byzantine Agreement

TL;DR

This paper introduces a scalable, fault-tolerant quantum Byzantine agreement protocol suitable for large quantum networks, using circular message gathering and quantum digital signatures to improve efficiency and practicality.

Contribution

It proposes a novel multiparty circular QBA protocol with quadratic communication complexity, compatible with existing quantum network architectures, and demonstrates its feasibility through simulations.

Findings

Achieves high consensus rates in satellite-to-ground quantum networks

Requires only weak coherent states, enhancing experimental feasibility

Supports large-scale, secure quantum blockchain applications

Abstract

Quantum Byzantine Agreement (QBA), a cornerstone of quantum blockchain, offers inherent advantages in security and fault tolerance over classical protocols, guaranteed by the laws of quantum mechanics. However, existing multiparty QBA protocols face challenges for large-scale deployment due to exponential communication complexity or reliance on complex multi-particle entanglement. To address this, we propose a multiparty circular QBA protocol that adopts a semi-decentralized architecture, leveraging circular message gathering and quantum digital signatures to achieve quadratic communication complexity and enhanced fault tolerance. Our protocol is experimentally feasible, requiring only weak coherent states, and is compatible with existing star-shaped quantum networks. Simulations conducted on a global satellite-to-ground network demonstrate that the protocol sustains high consensus rates among multiple users, even when employing different key generation protocols under realistic conditions. This work presents a scalable framework for large-scale QBA networks, establishing the foundation for a practical quantum blockchain that enables secure and fault-tolerant decentralized services.