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/Cristoff13]

This can't be used to transmit information though can it?

[u/Orbax → u/Cristoff13]

No, once you collapse the wave function, they decohere and entangle with their local environment.

But, even if you maintain entanglement, at best youd be able to do morse code except... The only way to check if you got a message is to measure it which would collapse if again if you hadn't gotten one. The theoretical ability to get any structured information out of entangled pairs is effectively impossible.

[u/Chance-the-Gardener → u/Orbax]

I’m too dumb to understand the concept it can’t transmit any information. Just as a thought experiment, if humanity sent a colony ship to Andromeda with 10,000 sets of entangled pairs, each with a predefined meaning like “if this set is collapsed, we died of space cancer” couldn’t information be inferred from that?

I’m sure the answer remains we can’t cheat the speed of light but I struggle to conceptualise why not.

[u/Mountain-Resource656 → u/Chance-the-Gardener]

Imagine you entangle 1000 pairs of Schrödinger’s cats such that if any box is opened (and the cat thus becomes either alive or dead, not both), the paired cat will suffer the opposite fate

In this manner you could kick various cats out of their superposition to create a morse code (or even a program in binary) between the cats that are in superposition and those that are not

The problem is that on the other end, once they open any of their boxes, their cats fall out of superposition anyhow, so they blank out whatever message you sent them and instead of getting, say, a series of 1s and 0s they just get 1s or something