Sort:  

Ah yes very nice I was thinking about this pathway last night.
It is a somewhat relevant concern.
But why stop there?
Why not just make up some other secret technology that can do the job today?

The ironic thing about the Quantum Computing angle is, just like the double-spend problem itself: it's entirely theoretical. The way quantum computing works is very niche with a narrow range. It can't just be assumed it will be able to perform this function.

And even if it can do the job: software development continues to prove itself exponentially faster than hardware development. We already have quantum resistant solutions ready to go live now. They are just more expensive to implement and everyone is waiting to be forced to use them. Capitalism is telling us that waiting to get attacked and fixing the problem in response is cheaper than fixing the problem now and never getting attacked.

So the reason I demanded everyone answer the questions (but nobody has yet) is that we come up with something like this:

  1. Attacker: USG

Now who are they stealing from and for how much? Is the project secret and nobody knows the USG is pulling this off? The problem here is two fold.

  1. There's no way these attacks pay for the cost of R&D on quantum computing.
  2. The USG is going to lose money on these attacks.

The United States Government has a much higher financial incentive to allow Bitcoin to flourish and simply legally confiscate anyone's Bitcoin who they deem to be a criminal. The USG holds BTC. The USG is in bed with characters like Blackrock who want BTC to succeed. Attacking it in this way is not an option when stealing the asset directly is far more profitable and legal.

Monero's XMR and privacy Zero Knowledge Proofs?

The one last final thought here is that quantum computing absolutely could completely destroy tokens like XMR. The government actually does have a reason to attack privacy coins hard. And if they can rig a quantum computer to pull this off that means they can secretly print as many privacy coins as they want and never get caught. Unlike BTC where everything is public: no one will even be able to know that an attack exists. Now that's a real threat worth exploring (later).

Agree on the USG motives, my intention was not to proof any point, just that QC should be added in the context, as we can´t be 100% sure. Wasn´t aware that such solutions are already in the drawer - even better then.
Agree also on XMR, therefore I am very cautious with buying this and likewise tokens.