Fix error to get descomposition

[josep-lumbreras]

[rrtucci]

Wat is the error joseplz?

[rrtucci]

Oh, sorry, I misunderstood. You mean, fix a parameter epsilon so that norm(u - approx_u) < epsilon. I haven't thought about it, but now that you mention it, it is a very natural request. I am ashamed I didn't do it to begin with.

[rrtucci]

It is a very good request, but will take a lot of time and work. I promise to do it someday...

[rrtucci]

I always use the Frobenius norm, but I am not very sophisticated about norms

[rrtucci]

The multiplexors decompose exactly into a huge number of gates but they can be approximated. I have included software to do a possible approximation of them. But it requires ancillary qubits

[rrtucci]

I think multiplexors and their approximation will be important in quantum AI