One particle doesn’t (can’t!) make an interference pattern. If only one particle comes through, then you will just get one spot on the detecting photographic plate (or whatever detecting apparatus you have). One spot is not a pattern!

However when the next particle comes through, it is highly likely to hit the plate at a different point. Then a third one comes through, again hitting a new spot.

But after hundreds come though, you will start to see that the spots aren’t randomly (i.e. evenly) spread, but that there are areas where they concentrate, and areas they all seem to avoid. This DISTRIBUTION of spots is the interference pattern.

I understand that the particles arrive in random order. Is that
after the first one, with each going through and making an
interference pattern, (either each the same, or different, or the
same in the long run?) Or is that only when their wave-functions are
apparently collapsed?

I don’t quite understand the EPR paradox or the quantum decoherence
theory. Could either one affect any of the answers to the above?

Warmest regards, Alex

This way of thinking is a departure from 2000 years of Western thought, 2000 years which brought us penicilline and the nuclear bomb and more stress-related illness than ever before. In QM this way of thinking has led us to a dead end. For 100 years physicists have been going round in circles trying to make sense of it, with no progress at all, while all the time the experiments have been confirming the message which is written loud and clear in the formalism discovered by Heisenberg and Schroedinger.

http://www.math.leidenuniv.nl/~gill/waveparticle.html

http://arxiv.org/pdf/0905.2723

In other words, no one has ever done the experiment exactly according to the mathematics. If they do, they will find out that the inequality is upheld.

To do the experiment appropriately (ensuring independence), you have to use a completely different setup for measuring each photon pair.

The reason is simple, in interpreting the experiments, people usually make a hidden assumption that all matter in the path of the photons (or electrons), including the detector, are static and uninfluenced by the photons (or electrons). However, if matter comming in ‘contact’ with the photons (or electrons) retains some ‘memory’ of the impact, the equivalence of the experiments to the theory breaks down.