Zixuan Feng, Zhengwei Liu, Fan Lu, Ningfeng Wang

We propose a unified classical simulation framework for quantum circuits, termed Quon Classical Simulation (QCS), built upon the diagrammatic formalism of the Quon language. Central to this framework is the introduction of magic holes, a topological feature that captures the global source of computational hardness in simulating quantum systems. Unlike conventional measures, the complexity of QCS is governed by the topological entanglement entropy associated with these magic holes. We show that Clifford circuits and Matchgate circuits are free of magic holes and thus efficiently simulable within our model. To capture the interaction structure of magic holes, we define a topological tensor network representation and develop novel skein relations and reduction algorithms to simplify circuit representations. This approach significantly improves the efficiency of classical simulations and provides a unified explanation for the tractability of various known quantum circuit classes. Our work offers a new topological perspective on the classical simulability of quantum systems and topological complexity.