Sophie SchmiegA very nice explainer why "if you're so worried about quantum computers, why haven't they factored 21 yet?" isn't a very convincing argument. Look at the labels of the graph, and how extremely close the various lines are for factoring 21 and 2048 bit numbers. Polynomial scaling remains polynomial, unfortunately, and by the time you can factor 21 you're almost ready to break RSA.
Dan Sugalski@sophieschmieg I suspect people will listen to cryptographers and quantum-focused computer scientists on this subject with the same focus and rigor they did when they said "no, no, don't roll your own cryptography, that's a bad idea".