Equivalence Checking of Quantum Circuits via Path-Sum and Weighted Model Counting

Wei-Jia Huang

Christophe Chareton

Yu-Fang Chen

Kai-Min Chung

Min-Hsiu Hsieh

Alfons Laarman

Jingyi Mei

Date of Publication

April 14, 2026

Centers

Quantum Computing Research Center

Publication Information

TACAS 2026

Topic

Quantum Computing

Source

PDF

Table of Contents

Equivalence checking of quantum circuits is a central verification task in quantum computing, ensuring the correctness of circuit optimizations, hardware mappings, and compilation pipelines. Among the primary symbolic methods for this purpose, the path-sum formalism provides a compact representation with powerful reduction rules that yield a canonical form for the classically simulable Clifford fragment, but confluence fails beyond the Clifford fragment. We introduce a new weighted model counting (WMC) encoding for path-sums and combine it with the existing path-sum reductions to obtain a verifier that is both complete and efficient. Our method applies reductions whenever possible and invokes the WMC-based decision procedure on the residual path-sum, yielding a complete semantic check up to a global phase. We implement the approach and evaluate it on standard benchmarks. Results show that the hybrid method outperforms either component in isolation and competes with state-of-the-art tools.