Non-zero Coefficients Removing Method to Improve the Ising Machine Solving Performance

The performance of an Ising machine in solving combinatorial optimization problems is significantly influenced by the energy landscape of an input quadratic unconstrained binary optimization (QUBO). Previous studies have shown that the number of non-zero terms in QUBO can control the energy landscape. In this paper, we propose a QUBO conversion method, which efficiently removes non-zero coefficient terms in QUBO to improve the solving performance of Ising machines. Our pro-posed method uses the removal ratio parameter, which defines the amount of removed non-zero terms, and efficiently removes the non-zero coefficient terms in QUBO. We confirm the effectiveness of the proposed method compared to the conventional method using the capacitated vehicle routing problem (CVRP) on an Ising machine. Experimental results demonstrate that our proposed method improves the path length in CVRP up to 17% compared to the conventional method.