  Quantum annealing is an emerging new platform for combinatorial optimization,
requiring an Ising model formulation for optimization problems. The formulation
can be an essential obstacle to the permeation of this innovation into broad
areas of everyday life. Our research is aimed at the proposal of a Petri net
modeling approach for an Ising model formulation. Although the proposed method
requires users to model their optimization problems with Petri nets, this
process can be carried out in a relatively straightforward manner if we know
the target problem and the simple Petri net modeling rules. With our method,
the constraints and objective functions in the target optimization problems are
represented as fundamental characteristics of Petri net models, extracted
systematically from Petri net models, and then converted into binary quadratic
nets, equivalent to Ising models. The proposed method can drastically reduce
the difficulty of the Ising model formulation.
