“…Sparked by the work of D-Wave Systems Inc. [1,2,3], a whole new field of optimization based on physical processes has emerged. Some examples are: digital processors based on simulated annealing [4,5,6,7] or other recently proposed algorithms [8,9,10,11]; coherent Ising machines implemented with pulse lasers [12,13,14,15,16,17], and other kinds of optical Ising machine [18,19,20,21]; simulated bifurcation [22,23] and other optimization using nonlinear oscillation networks [24,25,26,27,28]. Specifically, the development of hardware quantum annealers has stimulated new ways of tackling NPhard problems previously inaccessible.…”