  We construct an Ising Hamiltonian with an engineered energy landscape such
that it has a local energy minimum which is near to the true global minimum
solution, and further away from a false minimum. Using a technique established
in previous experiments, we design our experiment such that (at least on
timescales relevant to our study) the false minimum is reached preferentially
in forward annealing due to high levels of quantum fluctuations. This allows us
to demonstrate the key principle of reverse annealing, that the solution space
can be searched locally, preferentially finding nearby solutions, even in the
presence of a false minimum. The techniques used here are, to the best of our
knowledge, distinct from previously used experimental techniques, and allow us
to probe the fundamental search range of the device in a way which has not been
previously explored. We perform these experiments on two flux qubit quantum
annealers, one with higher noise levels than the other. We find evidence that
the lower noise device is more likely to find the more distant energy minimum
(the false minimum in this case), suggesting that reducing noise fundamentally
increases the range over which flux qubit quantum annealers are able to search.
Our work explains why reducing the noise leads to improved performance on these
quantum annealers. This supports the idea that these devices may be able to
search over broad regions of the solution space quickly, one of the core
reasons why quantum annealers are viewed as a potential avenue for a quantum
computational advantage.
