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Theoretically,if we perform the double slit experiment with single photon source then after a long time we can see the interference pattern same as it will be if we had done it with two coherent sources.

In case of the single photons propagating in space there is no issue of coherence as they are completely separate and emitted by the source after some finite time,in other word,they are incoherent.

But if we do the same experiment with incoherent source we won't be able to see any kind of interference pattern. Doesn't this violent the rules of statistical regularity?For single(incoherent) photons,the position they end up is probabilistic,but for lots of such incoherent photons coming at same time,the probabilistic nature remains no more.This shows that the position of each photon are not independent events.So there should be some interaction.Is there?

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  • $\begingroup$ "But if we do the same experiment with incoherent source we won't be able to see any kind of interference pattern" - This is incorrect. In the original double slit experiment, Thomas Young used a sunlight. Lasers weren't invented yet in 1801 - en.m.wikipedia.org/wiki/Coherence_length $\endgroup$ – safesphere May 24 '18 at 16:03
  • $\begingroup$ Okay,say our apparatus has length more than the coherence length.Even then by single photon source,we can can pattern,but not with a stream of photons coming at once. $\endgroup$ – user157588 May 24 '18 at 17:54
  • $\begingroup$ A single photon also has a coherence length. When the difference between two pathes is larger, single photons would not create interference lines - physics.stackexchange.com/questions/259116/… $\endgroup$ – safesphere May 24 '18 at 18:48

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