I would be grateful if someone could illuminate me on these questions: If two distant whole star systems are completely isolated, are they in quantum states to each other along with their all entangled particles? If single photon crosses over, does it carry and collapse all of the entangled particles from other system? Or in more probable scenario, If single photon is completely isolated from rest of the universe and considered as being in quantum state, is then the whole universe isolated and in quantum state to it? When it goes through slits but does not yet collapse to the universe screen, does it interfere with (to it) non-collapsed open and closed number of slits (rather then itself)? Does it then also interfere with whole entangled part of the universe before the collapse?