[powertower]

I've been following quantum computing since D-Wave made its press release some years back. Now I'm a complete skeptic.

The huge red flag I can't get over is if it is as so, why can no one validate it after all this time?

Why is there the proverbial "it works but not in the way you think it works" (i.e., quantum annealing) or "it works but we can use non-QM systems to simulate it faster, better, cheaper by a factor of a trillion"?

If QM computing was truly feasible (assuming that QM does have an underlining phenomena that is physically real), why are the results after all this time so fuzzy?

[Certhas]

Because you have to build the quantum computer in a world that is overwhelmingly classical.

There are no qualifiers along the lines of "underlying phenomena". It's simply difficult to get a stable enough interface between the classical and the quantum, so you can control it, while at the same time isolating it enough that it doesn't decohere to classicality.

Who knows, maybe reliable scalable quantum computation truly isn't feasible for some reason, but if you study the physics, the fact that this is so hard is not really a surprise.

[powertower]

But they have already solved the engineering problems (at least 10 years ago).

They already have "qbits".

The interface issues look to be 98% solved.

And the temperature cooling, the EM shielding, and everything else (that is outside the circuitry design and the physical chipset), a person with a budget of 80,000 USD can recreated in his garage.

Its the results I can't understand.

Why can't X qbits, in the time they stay coherent, produce results that agree with the mathematical analysis of the setup? Why is it always off by a factor so large that its not even productive for any task.

My understanding of it is not complete, this is why I ask. Is the interface issue only 2% solved (and not 98%), etc.?