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Let's assume that the ER=EPR conjecture is true, that is, if me and a friend take some set of entangled particles, divide them in half, separate them in space, and compress both halfs into black holes, that those black holes will connected by a wormhole.

It seems like this phenomenon can be used to communicate across the event horizon of a black hole. If me and my friend coordinate the time correctly, he could jump into a black hole, and then collapse his entangled particles. We could use the wormhole we just created to communicate superluminally.

Is there anything wrong with this?

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If you assume ER=EPR there is nothing more to ask, it is possible to communicate as you said. The point is that this assumption is highly non trivial, experimentally untestable (right now) and not embedded in any consistent approach to quantum gravity found so far, for instance string theory.

Regarding the conjecture, entanglement is an experimental fact while it's not clear if traversable wormholes can exist. In classic general relativity this typically requires violation of energy conditions, that the matter content around us seems to obey at a macroscopic level. Nevertheless energy conditions are violated by quantum physics, therefore quantum wormholes are conceivable. Notice that such a solution belong to a full quantum gravity theory, in which a geometric interpretation of space time should not be given for granted anymore.

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Whether ER=EPR or not, decohering entanglement does not transmit any information over any classical or quantum channel, so no, sadly one cannot do that.

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  • $\begingroup$ What do you mean by decohering entanglement? $\endgroup$ – psitae Oct 27 '17 at 4:46
  • $\begingroup$ When you "collapse" a quantum state, what really happens is that you become entangled with it, and the dynamics of the system becomes irreversible and the state is no longer coherent. See this wikipedia link. There is no information transmission to the other end. $\endgroup$ – SergeS Oct 27 '17 at 6:08
  • $\begingroup$ Sorry I still don't understand you. Where in this hypothetical situation do you see the need for decoherence? $\endgroup$ – psitae Oct 27 '17 at 6:10
  • $\begingroup$ Admittedly, I know more about quantum mechanics than wormholes. But as far as I know certain types of wormholes can be used to transport things (paper with writing on it, let's say) across vast distances of space. It seems like if you created a wormhole inside the black hole, you could use it to communicate. $\endgroup$ – psitae Oct 27 '17 at 6:12
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    $\begingroup$ @psitae what he's saying is specifically that you can not use entangled particles to communicate. $\endgroup$ – Asher Oct 27 '17 at 6:38

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