No idea what is going on.
If the second block is used to hide the card in the 4th slot, and we already know which slot the card is in, what exactly is happening in the quantum inversion step? Doesn't it already know where the card is?
Hey, Grover! Guess what. I only pretended to want to find the queen, but I really wanted the jack. How about you find the right card without me telling you which one I want.
@FritzSchober