For those of us who follow both Blockchain and Quantum computing, the question of how cryptographically secure the Blockchain can remain in a world with reliable Quantum Computers is top of mind.
This article: https://cointelegraph.com/news/quantum-computing-vs-blockchain-impact-on-cryptography explores some of the aspects of the intersection of these technologies and what the real threats to the hopes for a stable secure distributed ledger in the world of Quantum Computing might be.
Given Blockchain’s reliance on one-way mathematical functions that are hard to calculate “in reverse” a Quantum Computer in the wrong hands that can perform the factorization of a large prime number could wreak havoc with the Blockchain. An algorithm designed to provide the prime factorization of a large number http://news.mit.edu/2016/quantum-computer-end-encryption-schemes-0303 otherwise know as “Shor’s algorithm” was demonstrated to run on a Quantum computing device by researchers at MIT. They also showed that it is possible to scale their design to handle larger and larger numbers given that they could apply enough resources to their design. The design they have is not ready to scale to large primes yet (according to the article above) but they are confident that it can be in the future.
Even if such a computer may be years away it shows that Quantum technology is possible and could one day disrupt the world of Blockchain. Other researchers feel that BlockChain won’t stand still however. New algorithms can be applied for Blockchain instead of the same one-way hash reliant functions that are used with conventional computers today.
For those interested, more reading on the subject of Quantum computing is available here: https://www.nature.com/articles/d41586-019-02936-3
For information on Shor’s algorithm interested readers can inspect this link from wikipedia: https://en.wikipedia.org/wiki/Shor%27s_algorithm