Gordie Rose comments on recent experiments investigating whether D-Wave processors are quantum or classical:
It is common practice that whenever an experiment is reported demonstrating quantum mechanical (or in general non-classical) effects, researchers look for classical models that can provide the same results. A successful theory, however, needs to explain all existing experimental results and not just a few select ones. For example, the classical model of light with the assumption of ether could successfully explain many experiments at the beginning of the 20th century. Only a few unexplained experiments were enough to lead to the emergence of special relativity.
No classical model has ever been proposed that simultaneously explains all of the experiments [performed on the D-Wave processor].
The explanation that D-Wave processors are fundamentally quantum mechanical beautifully explains every single experiment that has ever been performed on them. The degree of agreement is astonishing. The results on the smallest systems, such as the individual qubits, are like nothing I’ve ever seen in terms of agreement of theory and experiment. Some day these will be in textbooks as examples of open quantum systems.
Read more here.