That is kind of misleading statement. What quantum computers change is not how many operations per second you could do, but how many operations you need to fact

That is kind of misleading statement. What quantum computers change is not how many operations per second you could do, but how many operations you need to factor large numbers. I believe that Bremermann's limit should also apply to quantum computers, but you are right in that example given for breaking cryptography is way off if you allow quantum computers.