  The coherent Ising machine is an optical processor that uses coherent laser
pulses, but does not employ coherent quantum dynamics in a computational role.
Core to its operation is the iterated simulation of all-to-all spin coupling
via mean-field calculation in a classical FPGA coprocessor. Although it has
been described as "operating at the quantum limit" and a "quantum artificial
brain", interaction with the FPGA prevents the coherent Ising machine from
exploiting quantum effects in its computations. Thus the question naturally
arises: Can the optical portion of the coherent Ising machine be replaced with
classical mean-field arithmetic? Here we answer this in the affirmative by
showing that a straightforward noisy version of mean-field annealing closely
matches CIM performance scaling, while running roughly 20 times faster in
absolute terms.
