As per the latest, Google has reached Quantum Supremacy. Meaning it could potentially decode an entire blockchain and...
YOUR PRIVATE KEYS...
Blockchains are secured through elliptic curve cryptography (ECC), just like encrypted user data and website traffic. Now the issue is that ECC is NOT "quantum-safe" meaning that a quantum computer could theoretically decrypt a user's private keys and forge transaction signatures.
Is this the end of Crypto?
I don't think so, but I'd love to hear your opinions too! (Especially the opinion of a cryptographer)
source
https://www.coindesk.com/what-googles-quantum-supremacy-means-for-the-future-of-cryptocurrencyHumanity currently does not have any technology necessary to create a quantum computer large enough to attack Bitcoin keys. It is not known how quickly this technology will advance; however, cryptography standards such as ECRYPT II tend to say that Bitcoin's 256-bit ECDSA keys are secure until at least 2030-2040. Blockchain companies: IBM, Google and a number of other technology giants are the current movers in developing quantum computing. It is likely that they will not enable users of quantum computing to crack bank-encryption or blockchain. To do so is illegal and would destroy those companies, by 2025, up to 10 percent of the global gross domestic product will probably be stored in blockchains. Quantum computing is a threat to technology blockchain because it increases the fundamental security assumption of elliptical curve cryptography, namely that computers cannot effectively factor large numbers.