Jet Tagging with a Graph-Based Quantum Neural Network: First Study on the Feasibility and Outlook

Machine learning, particularly deep neural networks, has seen widespread application in high-energy physics. Recently, quantum machine learning has emerged by integrating quantum computing with classical ML techniques. In this work, we propose the Quantum Complete Graph Neural Network (QCGNN), tailored for fully connected graphs and reducing computational complexity from O(N2) to O(N). We apply QCGNN to the jet tagging task in the datasets Top and JetNet for showing the feasibility, achieving AUCs of 0.932 and 0.822 via simulators, respectively, comparable to the leading classical models. On real quantum hardware via the IBM Quantum Platform (IBMQ), however, the AUC drops to around 0.5 due to quantum noise, indicating current devices remain impractical. The scaling behavior of QCGNN on computational complexity is further examined through runtime measurements on actual IBMQ machines.