>>16837947
We don't have the technology to build them or even know how. They essentially need to be constructed atom by atom. 3D layered transistors is the closest existing tech.
We don't have the technology to create a 'control unit' and software so they know wtf they are meant to do and not accidentally kill someone.
So a 'long time' is a hell of a lot longer than 10 years. Adding a zero is more realistic.