Question re: photon interference

[sanpkl]

I have been getting conflicting information so here are my questions, re:

1. Single photon interference
2. Interference between two photons
3. Two-photon interference

1. Some literature says that only single photon/particle interference exists.
Can two photons interfere with each other?

2. Can the "waves" of two photons interfere with each other?

By waves I mean as posited by the DeBroglie-Bohm (DBB) interpretation.

i.e. if two photons are sent separately through their own set of double slits;
as we bought the double slits closer would there be interference between the "waves" of photon A with that of photon B?

we are talking about - a total of 4 slits i.e. two double slits being brought closer.

3. Does two-photon = entangled photons/particles?

4. Do two-photon interfere?

5. Can they do so non-locally?

6. What is the relation between relation between two-photon interference and coherence?

 

[jerromyjon]

Coherence of wave phase leads to double slit interference, progressively diminishing intensity of constructive interference between not only 2 separate photons but with itself when alone as well. The thinner the slit the longer the interference range on the plane of observation. The distance between the slits is pertinent to the frequency of the wave. I see no benefit in complicating this simplified system by introducing more or less constructive or destructive interference with additional slits. Interference and entanglement are completely unrelated, unless you are trying to imply that interference is strictly non-local...