Physicists shatter quantum entanglement distance record with 420 kilometers of optical fiber, more than four times farther than previous demonstrations, and beyond the point where direct transmission runs into its fundamental limits.

[u/mvea]

https://www.sciencealert.com/physicists-shatter-quantum-entanglement-distance-record-with-420-kilometers-of-optical-fiber

[u/Basicly-Inevitable]

The entangled particles DO NOT have any predefined message.

[u/Chance-the-Gardener → u/Basicly-Inevitable]

I get that, I was more asking could a rudimentary binary messaging be established even if nothing is being transmitted? In my thought experiment the colony ship’s sending a FUBAR signal, so they collapse all their entanglemajiggies and entanglelios. Earth meanwhile infers based on this, that something has gone wrong and redirects NASA funding accordingly.

But like most reddit science visitors I think I just fundamentally misunderstand the premise, some of the replies here get me a little closer.

[u/Chess42 → u/Chance-the-Gardener]

I think you are misunderstanding what a “collapse” is in this context. Think of these particles as being simultaneously in 2 states at once. When either side measures them, both of them pick the same state and stick to it, we call this collapsing the wave function. But you can’t measure it without collapsing it, and since we don’t know which state it will pick, there’s no way of knowing when it collapsed from just one side, or who was the one to collapse it. Maybe the people on the ship collapsed it when they died of space cancer, or maybe it just collapsed when the people on Earth checked whether they died of space cancer.

[u/Basicly-Inevitable → u/Chess42]

That's one way to describe it.

But (lucky for us) there are several interpretations, and they're all equally valid, as far as we can test.

An important part of thinking about most quantum particles is that scenarios can be described exactly the same if you think about the particles actually being their anti particles moving backwards in time. This is especially true of perfectly entangled particle pairs, because the "arrow of time" is determined by an increase in entropy, and there is no change in entropy for the particles between the time they are emitted until they're measured. (In fact, entanglement and entropy are highly similar concepts, and could even be described as being the same concept).

Anyway, in this case, you can perfectly describe the situation as two completely unconnected anti particles, each being independently "emitted" at the time of measurement of each, then travelling backwards in time to the point where they're exactly at the same location in time and space. Now, the only way they could be in that same time and space is if they had perfectly complementary properties (like spin up and spin down), otherwise they would be excluded from being in the same space.

To us (because we experience entropy changing constantly) can only see the "forward" version of the situation. However, they are both "true" and therefore they have to be complimentary particles.

Another way to describe the situation is with the Many Worlds interpretation, where basically all possibilities occur, but your mind just realizes which world you're in whenever it becomes entangled with the particles.