  We introduce transverse ferromagnetic interactions, in addition to a simple
transverse field, to quantum annealing of the random-field Ising model to
accelerate convergence toward the target ground state. The conventional
approach using only the transverse-field term is known to be plagued by slow
convergence when the true ground state has strong ferromagnetic characteristics
for the random-field Ising model. The transverse ferromagnetic interactions are
shown to improve the performance significantly in such cases. This conclusion
is drawn from the analyses of the energy eigenvalues of instantaneous
stationary states as well as by the very fast algorithm of Bethe-type
mean-field annealing adopted to quantum systems. The present study highlights
the importance of a flexible choice of the type of quantum fluctuations to
achieve the best possible performance in quantum annealing. The existence of
such flexibility is an outstanding advantage of quantum annealing over
simulated annealing.
