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Comment by niederman | Hacker News Reader

While something like this could be an interesting idea for a sci-fi novel, this is not at all how quantum entanglement works. Entanglement doesn't make one particle "[adopt] the dilated time/gravity of its remote counterpart", it just refers to a perfect correlation of certain measurements of the two particles. For example, if you produce two particles that you know have zero total momentum, but don't measure the momenta of either individual particle, these particles are now entangled, because measuring the momentum of one particle to be p immediately tells you that the other particle's momentum is -p, regardless of distance. Time does not actually come into play at all here.

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interesting, content to be wrong based on an absolute ignorance of the topic. my laymans read of photon entanglement had to do with how it was described in quantum key distribution, where entangled photons maintained a kind of polarization state between each other over a long distance, where the observation of one of them caused a state change at the other "end". this idea of remote causality was what implied that the properties of one end of an entanglement could operate on another.

when I looked up whether other particles could be entangled in the same way, the analogy seemed to map, but the logical errors appear to be, a) assuming there is time between the entangled photons as there's no t in p = mv, b) then that there is time dependent information between the photons, then c) extrapolating that some property of black holes might operate on that relationship.

thank you for indulging!

> maintained a kind of polarization state between each other over a long distance, where the observation of one of them caused a state change at the other "end". this idea of remote causality

Operating on one half of an entangled pair does not transmit information to the other half. Therefore, the is no action or causation. Choices of vocabulary which imply otherwise are incorrect.

It also doesn't work by "hidden variables" - there isn't some secret value which we just don't know yet. So while it's probably least inaccurate to describe what happens in terms of our knowledge of the remote particle changing, is closer to the new facts we learned coming into existence as we learn them, rather than discovering an existing fact. Except that's also not quite right (information can never be created or destroyed).

Whether there is any kind of action on the entangled counterpart is not actually answered by quantum mechanics, and depends on the interpretation. For example, in the Copenhagen interpretation there is an action (measuring one half of the pair causes the others waveform to instantly collapse), but in the Many Worlds interpretation there is no causal action, because observation is just a new entanglement between the observer and the entangled pair system.

The math is clear that there is no information transfer.

The various interpretations are ways of trying to map what actually happens onto easily-understandable descriptions using standard classical-world vocabulary, which doesn't work very well because QM has fundamental differences from the macroscopic world that we live in and drive our language from. Where they disagree with eachother or with the math is because those mappings aren't perfect.

Just because there is no information transfer does not mean there is no action, it just means that this action does not break causality.

Redefining words like that makes the resulting explanations misleading outside the narrow circle who already know enough to be aware of and understand the redefinition.

Just another interesting point:

You can entangle two photons in a lab, keep one of them and send the other far away. For example, you can construct the pair in a way that both give the same polarization. If you measure one and the result is horizontal, then the result of measuring the polarization of the other is horizontal. If you measure one and the result is vertical, then the result of measuring the polarization of the other is vertical.

But a trick that is usually untold is that you can put a device in the path of the photon that is going far away to rotate it 90 degrees. The important part is that the photon in the lab is not affected. You can't make any measurement in the photon that you keep in the lab to check if the photon far away passed through the device to rotate it or not. But now if you measure one and the result is horizontal, then the result of measuring the polarization of the other is vertical. If you measure one and the result is vertical, then the result of measuring the polarization of the other is horizontal.

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