I would like to have a better grasp of the relation between quantum interference and state superposition that are linked in QM. For instance in the photon double-slit experiment the interference pattern is seen as a consequence of the superposition of the wave function(pure state), and when there is knowledge of wich slit must have been traversed i.e. by putting a detector the interference pattern is supposed to disappear switching to what one would expect in the case with defined trajectories without interference. But one slit experiments also give interference patterns if dimmer, so what seems to be happening is that the initial strong interference pattern is substituted by 2 one slit very weak diffraction patterns, wich makes sense if we think the interaction with the detector lowers the intensity of the pattern. In short, instead of interference versus no interference as complementarity would demand, we can also interpret the outcome of the experiment as double-slit interference pattern vs. two adjacent single-slit degraded interferences patterns.