measurement parts and computation parts can be on the same wafer but they are separate beings. in regular CPU you don't need measurement part, mostly. Transistors work precisely because they are made of semiconductors - due to some quantum mechanisms like https://en.wikipedia.org/wiki/Band_gap And transistors is where you loose most of energy. You can make capacitors out of superconducting material, and it could work out somehow for memory elements (at this moment these are made from transistors as well)