Suppose we managed to arrange a causality-violating transmission of data with hypothetical “superluminal cables” (SLC; see both links for respective descriptions) and expect, similarly to ideas popularized by David Deutsch, that it might result in communication from one “alternative reality” to another. Exact schemes may vary from the simple “send a word from a future and receive (the same or another) word in a past”.

Main questions are:

  • How should we analyse the data received to investigate possible differences between quantum interpretations?
  • How could experimenters reliably verify “several alternative realities” condition, debunking possible alternative explanations?

Any analysis of the setting leading to non-obvious implications, even speculative, can be considered a satisfactory answer. Ī only ask to describe carefully conditions of an experiment, see the two bottommost questions below.

Supplementary questions (Ī desire to consider them to some extent, but not require it for a satisfactory answer) are:

  • How could this condition (even short-lived) be exploited?
  • Would transmission of quantum information over an SLC offer some gains over transmission of purely classical information?
  • Should a difference between physical principles behind our SLCs (such as General Relativity vs a hypothetical anomalous Lorentz symmetry-violating solid) influence quantum aspects of the experiment??
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    $\begingroup$ Related by OP: physics.stackexchange.com/q/147076 $\endgroup$ – Kyle Kanos Nov 17 '14 at 14:51
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    $\begingroup$ First of all there is no superluminal communication, each device proposed during the years was shown to encapsulate a mistake. Your question is similar to "what would happen if the 2nd principle of thermodynamics didn't exist? But it exists. Next, between WHICH quantum interpretations you want to distinguish? Name them. There are some well investigated interpretations, and there are many ad-hoc. $\endgroup$ – Sofia Nov 17 '14 at 16:33
  • $\begingroup$ @Sofia: Ī do not assert a superluminal communication actually exists, but it can be conjectured. Which interpretations? Different flavours of MWI (including branching space-time, my preferred) on one hand, and Copenhagen and “realism” (a.k.a. hidden variables) on opposite hand. Ī’m not a good expert on quantum interpretations, but Ī hope that a causality-disrupting experiment can provide arguments in favour or against some other known interpretations too, notably von Neumann–Wigner. $\endgroup$ – Incnis Mrsi Nov 17 '14 at 16:54
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    $\begingroup$ Please see, I am not an expert in gravity - this would be your domain in this talk. I can only refer to the quantum theory, and some of the interpretations, those that I consider very well elaborated, not ad-hoc. There are many from the latter type. So, you ask what it would be IFF we could beat the light velocity? Then, YES, we could choose between Bohm's interpretation of the quantum theory (interpretation that I actually investigate) and the Copenhagen interpretation. But, there is NO superluminal communication. And that is to our luck. $\endgroup$ – Sofia Nov 17 '14 at 17:37
  • $\begingroup$ (continuation) If the superluminal communication existed, the world wouldn't exist. $\endgroup$ – Sofia Nov 17 '14 at 17:46

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