Q-reeus wrote
It may seem so with end-on view, but there is no coupling between swinging balls - just beat effects owing to the staggered string lengths thus oscillation periods. Two strings per ball provides lateral stability ensuring balls don't 'couple' via collisions. 'Wave-particle duality' there requires...uhmm...imagination!
Yes, I was too hasty and was wrong. There is no significant coupling. So the wave pattern is illusory. Well, it is a wave pattern at times but the balls are not engaged in any group collaboration or using feedback from one another.
As for the two links wrt the photon experiment, thank you. The second link referred to the effect being for a group of photons rather than showing a wave effect for a single photon. I had noted that myself previously, but accept that the experiment did not try to show single photon wave effects.
Some of the photos in the report seem to show variable numbers of peaks in the egg-crates? So that maybe answers my doubts. If the number of peaks can be varied then it is clear that each peak does not always correspond to a single atom in the nanowire. If there was such a correspondence I would think that the photons could be coming straight from the wire rather than from the SPPs (though I know very little about SPPs).