I think you're way off. Firstly, quantum computer isn't a silver bullet. How big it can scale depends (among other things) on how many qbits it can handle.

Then we need an algorithm that can theoretically solve a particular problem. So that might be: given an address, can I generate its private key? Usually it's: given a public key, if generated with sekp256k1, can I calculate its private key?

So far, I don't know that there's an algorithm for this although I have heard that there are algorithms that could theoretically crack other ECC (elliptic curve cryptography) algorithms, maybe that means all ECC algos?

Then we have the cardinal rule: DO NOT REUSE ADDRESSES. Until you spend from an address, your public key is unknown, instead your address is a hash of your public key. I don't know if there's a theoretical program that could crack that either.

Once you spend from an address, your security goes from hash+ECC to just ECC for any funds left at the same address or any new funds going into that same address.

So don't do that 🤷🏻