So I was reading this post by Ethan Siegel, which introduces a recent talk by Lee Smolin. In the article, Siegel outlines the EPR paradox (or something like it) and mentions that it is based on the following suppositions:
- You can create your pair of entangled particles at a particular location in space and time.
- You can transport them an arbitrarily large distance apart from one another, all while maintaining that quantum entanglement.
- Finally, you can make those measurements (or force those interactions) as close to simultaneously as possible.
Now, the "paradoxical" (or at least, "non-local") result of this that he mentions is that entanglement means you can know "information about a measurement... outside of your light cone".
But I was struck by the qualification in point 2 above. There, we're told that for the thought experiment to work, you have to be "maintaining" the entanglement, whilst simultaneously transporting them far apart. It seems to me, that for experimenter A with particle P to know that P is still entangled with particle Q throughout the journeys of both P and Q, then experimenter B (who has Q) would have to be continuously sending signals to A, letting them know that they haven't altered the entanglement of Q in some manner. If this is the case, wouldn't that mean Q would never actually leave P's light cone, thus contradicting the "paradoxical" non-locality result?
Based on the above, I have two questions:
- Is the above a correct interpretation of the thought experiment, or have I misunderstood something somewhere?
- If yes to the previous question, does this affect how the EPR paradox is usually explained/responded to by physicists?