I am learning how to make Grover's algorithm but the last cx gate needs to be the opposite way around. It always makes the top qubit the control, so how do you turn it around?
Just to add. If you do not have a possibility to switch control and target qubits, you can implement "upside down" CNOT with this circuit:
$$ (H \otimes H) CNOT (H \otimes H), $$
where $H$ is Hadamard gate and $CNOT$ is controlled NOT with control qubit upside and target qubit downside.