Quantum optimisation applied to the Quadratic Assignment Problem
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Abstract
This paper investigates the performance of the emerging non-variational Quantum Walk-based Optimisation Algorithm (NV-QWOA) for solving small instances of the Quadratic Assignment Problem (QAP). NV-QWOA is benchmarked against classical heuristics, the MaxMin Ant System (MMAS) and Greedy Local Search (GLS), as well as the Grover quantum search algorithm, which serves as a quantum baseline. Performance is evaluated using two metrics: the number of objective function evaluations and the number of algorithm iterations required to consistently reach optimal or near optimal solutions across QAP instances with 5 to 10 facilities. The motivation for this study stems from limitations of both classical exact methods and current quantum algorithms. Variational Quantum Algorithms (VQAs), such as QAOA and VQE, while widely studied, suffer from costly parameter tuning and barren plateaus that hinder convergence. By adopting a non-variational approach, this work explores a potentially more efficient and scalable quantum strategy for combinatorial optimisation. The results provide a direct comparative analysis between classical and quantum frameworks, characterising the average case performance of NV-QWOA. Our findings highlight the practical utility of quantum walks for complex combinatorial problems and establish a foundation for future quantum optimisation algorithms.