That seems suspect to me. Getting a working qc to reasonable scale is the hard part. Once you have done that most of the hard engineering problems are solved.

That seems suspect to me. Getting a working qc to reasonable scale is the hard part. Once you have done that most of the hard engineering problems are solved. I doubt doubling its size at that point would be very much of a problem. If we are making (uninformed) predictions, i bet we wont see QC solving 1024 bit RSA in the next 15 years (at least), but once it does it will only take a year or two more to solve 4096.