I'm doing some research about full homomorphic encryption (FHE). As I figured out, algorithms are implemented in circuits. I suppose that they are called circuits because the Holy Grail is to realize a NAND gate and then be able to do any kind of logic with that.
My question is: how does homomorphic encryption deal with conditions and jump operations? How could you calculate the nth item of a Fibonacci series recursively with a circuit?
Most of the manuals of FHE implementations don't talk about conditions and jumps. Is the idea that some instances do some preparation of the circuit before execution?