Quantum supremacy is but words for now. And although it is a possibility that is coming nearer in reality, there is nothing to be afraid of. This is only a big deal for FUD spreader and their victims. Quantum technology in computers is not monopolized by Google. The geniuses in the crypto world has already anticipated it long before it will even hit the market. In fact, steps have been done both in planning and in actual development that will somehow address this Quantum hype and FUD.
You don't understand me. Maybe you not read everything in the first post.
I think, google can change the software in this new kind of computer - and mine a little on the Bitcoin Network, to show, what a kind of efficiency this new computer has.
Maybe
with some similar computer can google (alone or with partners) decrease the mining power of China below 50% ... And then... As I wrote:
...
- firstly CPU mining. (technology A - public)
- then GPU mining. (technology B - public (fortunately) but technology A not an opponent)
- ... some other public technology, pools, merged mining, and so on...
- in future: technology X coming - (not published - owned by some (or one) persons/firms/...) AND (technology A and technology B and other public technologies aren't an opponent) - the controll of members of Bitcoin forum over bitcoin (and our "money") loosed!
...
You do not understand how the protocol adjust the difficulty when massive amounts of hashing power are introduced. The difficulty will simply go up and it will become a lot harder for people with powerful computers to compete with massive mining farms.
Also, even if Quantum computing are introduced, stronger encryption will be implemented to protect people's coins. There are stronger encryption out there already, but it was not practical at the time to use it, because there were nothing strong enough to decrypt it.
Remember, Bitcoin is a piece of software and software can be changed to adopt to the changing needs or threats to it's users.