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**Is "quantum indeterminacy" a result of experiment design?**

Stemming from a debate about free will, I, a total lay person, have been doing some reading on quantum indeterminacy (QI). I have come up with some questions, I hope this forum is an appropriate place for them.

Basically the question is this: where does the idea of QI come from. The two scenarios that seem to pop up most often are Schrödingers cat and the two-slit electron experiment. But in both cases it seems to me that the indeterminacy that shows up is exactly what was designed into the experiment.

In case of the cat the design incorporates a known indeterminate element: the decay of an atom. We do not have a model that will predict the exact time when a given atom will decay, but we do have a statistical model, and that model is incorporated into the cat experiment. That model predicts that, if we open the box at t=Lambda, we have a 50% chance of a dead cat. Before we open the box we of course don't know the state of the cat, but that is what was designed into the experiment. How does this show any indeterminacy beyond that which was designed into the experiment?

With the double slit experiment we seem to have a similar situation. The indeterminacy designed into the experiment is that we don't know exactly which slit a given electron will go through. But we do know that 50% of the electrons will go through one, 50% through the other slit. The actual probability distribution turns out to be a wave function, which is perhaps a bit unusual, but no more than that. As a result the distribution of electrons on the detector screen displays an interference pattern. So far I fail to see any indeterminacy beyond what was designed into the experiment.

We can then change the experiment by removing the indeterminacy: we add some sort of apparatus that tells us through which slit each electron passed. This apparently changes the probability distribution from a wave to a classic particle yes-or-no distribution. OK, so that is maybe strange, but I still see no indeterminacy here.

In both cases the outcome of the experiment is completely predictable. In the first case we have a probabilistic experiment (we don't know which slit each electron goes through), hence we get a probabilistic outcome. Indeterminacy would only pop up if the interference pattern was not consistent. When we change the experiment such that we remove the indeterminacy, we get a result that is equally predictable and compatible with the new experimental set-up.

So where does this term "quantum indeterminacy" come from? I must be missing something here.

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