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/