I know there are other questions i.e. Do quantum computers manufactured by D-Wave Systems, Inc. work? , What can the D-Wave quantum computer do? , etc. But I can't seem to find my answer. What is getting in the way of determining if D-Wave is a quantum computer? Why can't we just analyze the way they built, and see if it's quantum? Is there a problem with patents getting in the way? Why can we still not tell?
Why can't we just analyze the way they built, and see if it's quantum?
because the environment can easily get in the way and prevent the quantum effects from creating the speedups they're meant to. Basically you can try to build a quantum computer and end up with a classical computer by mistake that does the same thing (but slower) if it wasn't built carefully enough. The only way we can determine whether it worked for sure is by seeing if the way it runs in practice could only be produced by a quantum computer. So the relevant question is "Can the performance we're seeing be explained classically?" which seems to be a 'yes' so far. It's not so much that things are getting in the way of testing, its that D-wave's claims about what it can do are never substantiated by independent tests. It is being tested, and found to be essentially classical. What might come out of the various improvements they're going to try over the next several years is unknown, but their track record isn't great so far.