It is my understanding that Einstein produced the EPR paper to necessarily elucidate the existence of physical properties that could not exist prior to measurement. That was his assumption which was later proven incorrect. However, there is another consequence of quantum mechanics: quantum tunneling. Did he not know about this? Was it unaware at that time that tunneling exists or was there no empirical evidence to support tunneling?

Here's why I think quantum tunneling would've dissuaded Einstein for making his case against quantum mechanics. If position eigenstates are really determined prior to measurement, then it seems to be no reason whatsoever why you would expect a particle to cross a high energy barrier unless you accept the probabilistic wavefunction as the correct description for the position eigenfunctions.

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    $\begingroup$ As you can see from the linked article, quantum tunneling was discovered in the late 1920s, and the EPR paper is from 1935, so yes, it was well-known by then. Einstein's objections to quantum uncertainty were philosophical and did not depend on its specific manifestations, see Why did Einstein oppose quantum uncertainity? Einstein accepted quantum theory formalism, but considered it incomplete, so no experiments could prove him "incorrect" in principle, even as most physicists did not accept his philosophy of reality. $\endgroup$
    – Conifold
    Apr 6, 2020 at 17:39
  • $\begingroup$ @Conifold Alright, that could qualify as an answer, however that doesn't quite explain why Einstein didn't consider this as an edge case for a purely deterministic theory. Without probability of wavefunctions, the phenomenon of tunneling would've never been discovered theoretically. That alone provided an empirical test to reinforce the uncertainty principle. $\endgroup$
    – Weezy
    Apr 6, 2020 at 17:49
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    $\begingroup$ And without Newton's action at a distance theory of gravity Neptune would not have been discovered. Which did not prevent it from being an incomplete theory later replaced by general relativity. Same with using ether to predict diffraction of light, etc. Being phenomenological and/or incomplete does not prevent theories from aiding discovery. It does not mean that what they postulate in the formalism maps to reality. $\endgroup$
    – Conifold
    Apr 6, 2020 at 19:35


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