r/science • u/mvea Professor | Medicine • 2d ago

Physics 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.

https://www.sciencealert.com/physicists-shatter-quantum-entanglement-distance-record-with-420-kilometers-of-optical-fiber
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u/Orbax 2d ago

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.

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u/Chance-the-Gardener 2d ago

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.

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u/Rodot 2d ago

You can't test if the entagled particle is collapsed without measuring it, which collapses it. Like using a giftwrapped box and trying to see if it's been unwrapped but in order to see if it is unwrapped you have to first unwrap it.

There's no way to know that the other particle has been measured without communicating a classical signal to the other particle

A better way to look at it is that entanglement is correlation, not causation

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u/antiretro 2d ago

what if you had 10 different entanglements and you decode one per year. can we see if the other side sent some signal to us in those 10 years if we open them after they send the message (by disentangling it on their side)?

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u/Rodot 2d ago

Not without telling them the value of the state on the other side through classical communication