One can add different components and filters in one of the paths. By adding a filter that flips the magnetic moment of the neutron in path B (lower branch), it leads to a new superposition state: neutron taking path A with a magnetic moment pointing right, plus the neutron taking path B with the magnetic moment flipped pointing to the left. This state is called a postselected state. As the states cannot longer interfere coherently due to this modification, the neutrons can exit through the two ports, either to the right reaching the detector or exiting towards the dark port.