Perhaps reality is actually only approximated by the wave function but reality is something else under the surface which means quantum computers may need to be reconsidered.
2. Everything after the first sentence doesn't make sense. Any system that implements a restricted class of unitaries and features local measurement as described by Born's rule can efficiently solve problems in BQP. We have no reason this should apply to 10 qubits and not 1000.
The theory of quantum mechanics has been completely predictive in materials and has resulted in the most accurate predictions in nature (Anomalous magnetic dipole moment to a part in a trillion.) It doesn't matter if the theory is "Macroscopic" or whatever, it's predictive and within the constraints of its predictions you have known computational power up to problems in BQP. Whether BQP=P is an open question, but as is P=NP.
Known problems are things like wiring, materials science/sources of noise -- eventually including things like cosmic rays. It should work and we have no reason to think it shouldn't due to fundamental limitations of the natural world. It is, however, one of the hardest scientific things humans have ever tried to do so far. To say it'll definitely work is hubristic.
[1] https://plato.stanford.edu/entries/qm-collapse/#ContSponLoca...
[2] https://en.wikipedia.org/wiki/Ghirardi%E2%80%93Rimini%E2%80%...
When I talked about a "fundamental limit on how big you can make a quantum computer" I wasn't talking about it's physical size, I was talking about the number of mutually entangled qbits it contains, and the amount of time it is able to maintain those entanglements in a coherent state.
There's apparently noise in the system - how do we know that the reality is different to the model, and what we are putting down to noise is actually reality being different to the model? Kind like Einstein's correction of Newton.
That being said, if physics derisking failed, it seems really unlikely to me that it would be because quantum mechanics itself was wrong as opposed to there just being some unforseen problematic error mechanism that was consistent with quantum mechanics. Finding a flaw in quantum mechanics itself would be a scientific revolution, which would be awesome, but those are also pretty rare.
I also think it's a little telling that people keep thinking it's the philosophically unsatisfying parts of quantum mechanics that are going to break, when entering a new regime. It smells of confirmation bias.
Disclaimer: am on google quantum team.
I highly recommend reading [1] for an overview of the various skeptical viewpoints on quantum computing. Note that, while Aaronson argues most of the initial arguments are trivially wrong, he admits that whether or not error correction is fundamentally impossible is an open question.
We can keep solving the engineering challenges, but the universe might simply not allow us to get a return on investment with every additional qubit.
QC in contrast must exist or else QM is fundamentally wrong - not incomplete, but wrong.
Up to 12 qubits or so.
> Perhaps reality is actually only approximated by the wave function but reality is something else under the surface which means quantum computers may need to be reconsidered.
Possible, that reality is only approximated, and that approximation breaks down at more qubits. However, that would be the more exiting outcome, since then we have an experiment that gives us a window into a post quantum theory.
We know its possible to have a fusion reactor, we would just have to dump enough mass together to build a sun. Hopefully we can make it more cost effective.
There isn't a natural phenomena that solves a problem by encoding it and (ab)using quantum physics.