Quantum Computing will NOT even touch cryptocurrency
If you spend some time training on the 5 Qubit IBM training system you will learn in the literature that it can only reduce the problem set by a SQRT.
This is a reference to hashing algorithms and Grover's solution.
Shor's solution breaks public key cryptography:
https://en.wikipedia.org/wiki/Shor's_algorithm"If a quantum computer with a sufficient number of qubits could operate without succumbing to noise and other quantum decoherence phenomena, Shor's algorithm could be used to break public-key cryptography schemes such as the widely used RSA scheme."
All cryptos using ECDSA are highly vulnerable.
The ECDSA public key isn't exposed since most cryptos using its hash as public address. Public key itself is not stored in blockchain.
So back again to Grover's.