Trying to understand coherence and entanglement and have some questions: 1. Do incoherent photons interfere? a) Single particle interference through double slit b) Multiple photons through double slit Is it that the interference pattern in the above cases is not a clear fringe pattern however there is still interference? 2. Why does coherence increase when light is passed through a pin hole? 3. Why does brighter light have higher coherence? 4. What does coherence within a single photon mean? 5. Can coherence be changed (is it reversible) within the same photon? i.e. Is entanglement changeable between two photons? i.e. can the experimenter play with coherence and entanglement with the same set of entangled photons? i.e. decrease coherence and watch the effect of increased entanglement, Increase coherence and watch the effect of decreased entanglement? 6. In a single particle, double -slit experiment are the wave-functions passing through each slit assumed to be entangled with each other? in the case of an "in-coherent" photon?