(Guardian.co.uk) The discussion from the Guardian’s John Naughton opens with an amusing look at Google’s ‘quantum supremacy’ document on the Nasa website – and its disappearance shortly afterwards. Conspiracy theorists immediately suspected that something sinister involving the National Security Agency was afoot. Spiritualists thought that it confirmed what they’ve always suspected about quantum phenomena. (It was, as one wag put it, a clear case of “Schrödinger’s Paper”.) Adherents of the cock-up theory of history concluded that someone had just pushed the “publish” button prematurely.
The author segues to the seriousness of quantum supremacy. The security of our networked world depends on public-key cryptography – the encryption that protects communications, bank accounts and other sensitive data. At the core of this approach is the fact that factoring very large numbers takes a long time. In principle, industrial-scale quantum computers could make a mockery of all this – but that’s in theory.
The second caveat is that quantum machines would be able to crack some codes but not all possible codes. The public-key codes that would be vulnerable happen to be the ones we use to secure online transactions and to protect data. But private-key encryption will probably still be invulnerable. And researchers have been working on new types of public-key crypto that no one knows how to break – even in principle – after two decades of trying.

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