I have a simple question on double slit experiment, In double slit experiment, after the light rays pass through the slits, place two beam splitters (down converters) which split the light into two rays, one going towards the screen and other going orthogonal to it. Now my question is do we get interference on the screen? (Remember that I do nothing to the orthogonally travelling light. I leave it undisturbed) The simple answer seems to be 'Yes' because we are in no way trying to obtain 'which-path' information. We just split the beam. But I believe the answer is 'No'. I would like to know the correct answer. If I am correct, placing reflecting mirrors do not affect interference. Similarly placing beam-splitters also should not affect it (But this contradicts at times). But placing polarizers do affect interference because it gives an 'identity' to the photon.