  We use exact enumeration to characterize the solutions of quadratic
unconstrained binary optimization problems of less than 21 variables in terms
of their distributions of Hamming distances to close-by solutions. We also
perform experiments with the D-Wave Advantage 5.1 quantum annealer, solving
many instances of up to 170-variable, quadratic unconstrained binary
optimization problems. Our results demonstrate that the exponents
characterizing the success probability of a D-Wave annealer to solve a QUBO
correlate very well with the predictions based on the Hamming distance
distributions computed for small problem instances.
