Quantum computers that can do fast factorisation have been demonstrated, they just haven't yet been able to factor large enough numbers to be dangerous.
> they just haven't yet been able to factor large enough numbers to be dangerous.
According to [1], the current highest factorization using Schor's algorithm is 21=3 * 7 published in 2012, up from the 15=3 * 5 that was demonstrated in 2001. This pace is not all that promising.
Sure, there are other quantum factorizations, but they are either stunts (work only for very narrow classes), or are based on a different algorithm than Schor, which does not show hope to scale up.
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Factoring by Quantum computers able to implement Shor's algorithm (which is the proposed apocalypse for the family of public key algorithms used today) so far isn't just short of "dangerous" it's short of what you'd expect school children to achieve. 21 is 7 times 3. Really, I'm not exagerrating, that's what they've achieved.
As with the work done to try to figure out how we should handle a big rock coming our way, work on post-quantum cryptography is justifiable because it's something we would really regret not working on if it suddenly becomes necessary and it's not _that_ expensive. But just because the threat justifies relatively modest research expenditure doesn't make it worth a newspaper article that will invariably distort the facts and confuse more than it illuminates.
According to [1], the current highest factorization using Schor's algorithm is 21=3 * 7 published in 2012, up from the 15=3 * 5 that was demonstrated in 2001. This pace is not all that promising.
Sure, there are other quantum factorizations, but they are either stunts (work only for very narrow classes), or are based on a different algorithm than Schor, which does not show hope to scale up.
[1] https://crypto.stackexchange.com/questions/59795/largest-int...