Quantum computers have long been dubbed as the Achilles’ heel of Bitcoin and the whole cryptocurrency industry.
"As the name itself suggests, the whole industry revolves around cryptography. This is how a decentralized system can actually be built – using cryptographic methods to shield users from attacks, misappropriation and counterfeit..."
https://beincrypto.com/quantum-computers-do-not-currently-threaten-bitcoin-and-maybe-never-will/
The very earliest bitcoin addresses were actually vulnerable to this. Today, we pay to a Public Key Hash, or a Script Hash. that is, we hash the cryptographic item (twice even), and anyone that can reproduce that hash can spend. The combination of Elliptic curve cryptography and secure hash makes Bitcoin amazingly hard to crack! As if cracking ECC alone wasn't hard enough ;)