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It is stated in this poster from a 2007 Sciam article (link below) that an observation is not required in a quantum eraser experiment:

"The fringes do not appear if the particles interact with something that could thereby be used to ascertain each particle's location at the slits. For example, a photon might scatter from the particle, and reveal that it went through the right-hand slit. The photon need not be detected - all that matters is that the 'which slit?' information in principle could be determined if it were to be detected."

So it seems that only the existence of the routing information makes a difference. Is this true, and if so, could the experiment be automated entirely?

https://static.scientificamerican.com/sciam/assets/media/inline/DD39218F-E7F2-99DF-39D45DA3DD2602A1_p95.gif

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The Sciam article is for particles like electrons or small molecules that exhibit wave behaviour. By automation I assume you mean that the experiment set up so it is repeatable over and over again, i.e not much human intervention just data collection and that they get consistent results. The answer to this is yes.

There is a another purely photonics version of this experiment where polarizers and employed at the slits to get which way info. That info disappears when info is detected about the beam. A way to understand it is to think of the path of the particle or photon to be entangled with the apparatus, when you make an observation you upset the entanglement.

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  • $\begingroup$ Thank you. And if there was no data collection, no human intervention at all. Is it true that according to theory, or as far as we know from other experiments, the experiment would do the same thing. That is: no routing information exists leads to interference pattern, routing information exists leads to no interference pattern? $\endgroup$ – David Sep 5 '18 at 21:23
  • $\begingroup$ That is correct but its kind of a philosophical point as well ... if we (humans) never observe it what's the point? What I like about this experiment is it shows (in my mind anyway) that wave function creation (also known as a photon in an EM field) can also include electrons in the materials/atoms that generated the photon to begin with. The wave function will react to changes over distances. $\endgroup$ – PhysicsDave Sep 5 '18 at 23:16
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The observation is definitely not tied to a human being. A detector (or collection of detections from several detectors) will suffice when interpreting the data. In this particular example, it is noteworthy that the system itself has embedded the "weirdness" of the particles behavior.

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