Bitcoin Blockchain & Quantum computing

[NeunMalSechs]

What will happen to Bitcoin (and all other alt coins) once quantum computing becomes operative?

I know, that all of todays cryptology (as we know it) will become obsolete once quantum computing is operative, because all keys can be cracked in minutes. I assume, that operative quantum computing is still some years away (beteen 5 and 20 years is my guess) but I would like to understand what the impact will be.

I guess its save to assume, that digital / crypto currencies will still be relevant. But how might the transition look like? I am looking for thoughts on this questions:

1.) Can the SHA-256 algorythm in the bitcoin protocoll be replaced by some other (quantum computed) algorythm? Or is this part of the unchangeable bitcoin core? If it can be replaced - how would this be done and is someone working (researching) on this?

2.) Is someone working (researching) on a quantum computing based cryptology approach? Who? Where?

3.) Would it be thinkable to have a smooth transiton between bitcoin and a follow up currency? Or will it be a "run for your life" thing, letting bitcoin exchange rate collapse?

4.) Is it even possible to develope a new currency before quantum computing is operative? Because once its here, bitcoin is not secure any more, but a new currency might not be available if development can not start without quantum computing being operative.

5.) Any technical sources that highlights the issue are welcome.

Thanks for your Input

[miffman]

I'm only really able to answer 1). I've read somewhere that SHA256 can be replaced with some other stronger algorithm with a hardfork. It's not something that cannot be changed. As for a quantum-computer secure algorithm, I'm not too sure what kind of work is being done there.

[Rmcdermott927]

NIST over the past few weeks put in a request for post-quantum algorithms to be developed. They could then be implemented into Bitcoin via a hard fork.