An Ising model is a statistical mechanics model for explaining the behavior of a magnetic material. An Ising model is defined by plural spins each of which has a binary value, that is, +1 or −1, interaction coefficients between spins, and external magnetic field coefficients each of which belongs to each spin. Using an Ising model, energy corresponding to the Ising model can be calculated from a given spin array, given interaction coefficients, and given external magnetic field coefficients. The search of the ground state of an Ising model corresponds to an optimization problem to obtain a spin array that makes the energy function of the Ising model minimum. Here, it is known that the search for the ground state of an Ising model the topology of which is a nonplanar graph is an NP-hard problem.
The search of the ground state of an Ising model also corresponds to a maximum cut problem that is known as an NP-hard graph problem. Such a graph problem can be used for wide applications such as the detection of a community in a social network and the segmentation in image processing. Therefore, if there is an electronics apparatus capable of executing the search of the ground state of an Ising model, the apparatus can be applied to various problems.
Patent Literature 1 discloses a quantum calculation apparatus of an Ising model and a quantum calculation method of the Ising model. In addition, Nonpatent Literature 1 discloses a semiconductor apparatus that executes simulated Annealing.