I put the word "some" in front of "crypto" for a reason.
There is some crypto that we know how to break with a sufficiently large quantum computer [0]. There is some we don't know how to do that to. I might be behind the state of the art here, but when I wasn't we specifically really only knew how to use it to break cryptography that Shor's algorithm breaks.
Nope. Any crypto you can break with a real, physical, non-imaginary quantum computer, you can break faster with classical. Get over it. Shor's don't run yet and probably never will.
You are misdirecting and you know it. I don't even need to discredit that paper. Other people have done it for me already.
This is like asking whether $500 billion to fund warp drives would yield better returns.
Money can't buy fundamental breakthroughs: money buys you parallel experimental volume - i.e. more people working from the same knowledge base, and presumably an increase in the chance that one of them does advance the field. But at any given time point, everyone is working from the same baseline (money also can improve this - by funding things you can ensure knowledge is distributed more evenly so everyone is working at the state of the art, rather then playing catch up in proprietary silos).
True quantum computing in the sense that most people would imagine it, using individual qubits in an analogous (ish) way to classical computers, has not reached a useful scale. To date only “toy problems” to demonstrate theoretical results have been solved.
They can break some cryptography... other than that... what are they good for?
There's some highly speculative ideas about using them for chemistry/biology research, but no guaranteed return on investment at all.
As far as I know... that's it.