That isn't implied. A particle pair collapsing from a superposition of to one of its eigenstates upon measurement, is a change in the particle in one location that instantaneously affects the other for all intents and purposes. This still doesn't allow you to use this to transfer information from one point to another faster than light due to the way nature lets you observe and manipulate things (e.g. the no-cloning theorem crucially prevents you from by-passing the permanence of quantum collapse).
But the effect is very much real. Much more real than you might think.
You can't use it to communicate faster than light, but you absolutely can use it to coordinate faster than light. It's called quantum pseudo-telepathy. See for example the Mermin–Peres magic square game. Two players with two pairs of entangled particles can win this game with 100% probability even if they're lightyears apart, whereas players without this resource can't win 100% of the time if they're separated (e.g. by adding sufficient distance and a time limit to the game).
> This isn't implied. A particle pair collapsing from a superposition of to one of its eigenstates upon measurement, is a change in the particle in one location that instantaneously affects the other for all intents and purposes.
If you were to use this explanation to anyone that isn't already deeply familiar with how quantum entanglement works, the "instantaneous" part of it would absolutely imply either FTL communication or at the very least the idea of a hidden variable behind the particles at the point of entanglement. And that's assuming they even understand what an "eigenstate" even is.
The wording is fine. Making people realize that a FTL effect is happening is more important than telling them that due to the no-cloning theorem we can’t directly observe it.
1. Observing the event or trying to clone entire states isn't what anyone was worried about. It's the idea that you could set even one bit to measure later (which is trivial to do with a normal particle).
2. There's no tradeoff here. "more important" doesn't matter. It's easy to make a sentence that states an FTL effect occurs and that data can't be sent.
Saying it happens "instantly" implies a preferred frame, but the process is invariant under Lorentz boosts.
It also assumes a specific way of representing the quantum state (eg a state vector over all parts) whereas other representations like Feynman paths have no corresponding notion of an instant change.
What I'm trying to convey is that the statement "entanglement is instant" is implementation dependent. You can meet the specifications of quantum mechanics using a simulator where entanglement is instantaneous, but you can also meet those specifications using a simulator where entanglement is not instantaneous or where that concept doesn't even type check.
What we can objectively say is that entanglement doesn't care about the distinction between time-like separation and space-like separation. If two non-communicating parties are entangled and they perform an experiment, there is no observable distinction between the cases where one of them goes first or the other goes first or in whether there is time for light to travel between them in the delay between their two parts. But that is much looser than requiring the effect to be instantaneous in some unspecified frame, because only requiring that there's no observable distinction is a much looser constraint than specifying that it must be instantaneous. And the only thing that we can experimentally verify is the looser constraint.
But the effect is very much real. Much more real than you might think.
You can't use it to communicate faster than light, but you absolutely can use it to coordinate faster than light. It's called quantum pseudo-telepathy. See for example the Mermin–Peres magic square game. Two players with two pairs of entangled particles can win this game with 100% probability even if they're lightyears apart, whereas players without this resource can't win 100% of the time if they're separated (e.g. by adding sufficient distance and a time limit to the game).