If you're curious about using a ring bigger than the integers, the question is how to write (a+b)^2 * (c+d)^2 as x^2+y^2, for some integers x and y?
Hint: Use Gaussian integers.
Very helpful. Thanks Peter!
Peter Selinger and Eddie Schoute in a bar looking at Peter's notepad while Peter explains that most of Shor's algorithm was already known to Fermat. Except the quantum part.
And the day ended in the pub where Peter Selinger taught us that in number theory, you should always use a bigger ring.
