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TheDreadfulGreat t1_j5nincp wrote

Reply to comment by DonaldFauntelroyDuck in Do you think we will ever be able to communicate faster than the speed of light using entangled particles? by DefenderOfTheButter

Almost positive this has already been done. Only saying "almost" because I wasn't in the (well documented) room.

Entangle two particles, whatever happens to the first happens to the second...regardless of distance separating them.

https://en.m.wikipedia.org/wiki/Quantum_entanglement

If a person were to say, alter the spin or charge of a quantum entangled pair of particles, the same alteration happens to the entangled pair....in real time. No delay, regardless of distance.

The Chinese have already used quantum entangled particles to demonstrate FTL communication between their terrestrial comms and their space station. Old news.

This is not a question of whether?...it's a question of what's next?

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thegagis t1_j5nlf4y wrote

You can MEASURE the spin or charge of an entangled pair, but altering it to a spesific outcome means you break the entanglement. The FTL communication is properly impossible.

It may have uses in quantum computing or cryptography, but communication it is not.

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DonaldFauntelroyDuck t1_j5o8ubj wrote

I am pretty sure that i read an article that with bose-einstein Kondensator you can actually transmit information between them. The whole point is the measurement on the other sire becoming identical. With photons entangled pairs you will need some back channel however with larger entangled quantum entities I believe it was shown to actually be able to transmit the information Thus was shown by schrödinger for example https://plato.stanford.edu/entries/qt-entangle/

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Adeldor t1_j5oy5tv wrote

I had a look at your link, but didn't see anything indicating useful FTL communication.[*] Further, by all understanding, any such communication between points in our universe - even if attempting to bypass actual traversal through this space - results in time travel, raising the specter of causality violation. Regarding the paper's reference to "many worlds," that might be the only way around said violation. But again it would not be useful, as no information within the same timeline would be transferred.

[*]: If I missed it, could you highlight or quote the text?

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DonaldFauntelroyDuck t1_j5pcg2g wrote

My understanding of

In the second part of the paper, Schrödinger showed that an experimenter, by a suitable choice of operations carried out on one member of an entangled pair, possibly using additional ‘ancilla’ or helper particles, can ‘steer’ the second system into a chosen mixture of quantum states, with a probability distribution that depends on the entangled state.

Is that actually you can change one system by changing the other.

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Adeldor t1_j5pfez1 wrote

My understanding here is that the ancilla are themselves limited by the speed of light, thus limiting communication speed to the same, and this experiment's goal was to (dis)prove the apparent instant simultaneous collapse. But I'm very open to correction here.

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DonaldFauntelroyDuck t1_j5ph0zq wrote

I do understand this a bit different and would expect that this would be actually possible. According to the relativity theory the point is that the "spooky entaglement" happens at identical times everywhere.

Maybe this paper is better:

https://jqi.umd.edu/news/first-teleportation-between-distant-atoms

or this

https://www.engadget.com/fermilab-quantum-teleportation-report-221002594.html?guccounter=1&guce_referrer=aHR0cHM6Ly9kdWNrZHVja2dvLmNvbS8&guce_referrer_sig=AQAAAHDBA8t0ynTc7F_k2JnVOXRUIpUzqyyj6BpK9DaTzOdvmk8vuKSctX_ht_-IcN0TKwrrHOjDoS1-qEqAX-KVang2lQi9Sj0c0p3VyhlgiwMLK434JEf0guL7cBMpnQhja0vtR8N0LNGXNXnsvFjOJcNPnY2mAltkGs5yJGxlGIqn

"teleportation" is in my understanding "timeless" as it happens between entagled entities.

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Adeldor t1_j5pkthe wrote

While the teleportation is instantaneous, I don't think there's any way to bypass the need for ancilla to be transported "classically," which are required for the Bell measurements at the receiver.

And there's still the causality problem (manifest here as "information causality" - PDF). Of course, one should never say never, but it seems there's always a fundamental roadblock when it comes to FTL, regardless of the path taken.

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DonaldFauntelroyDuck t1_j5q1p39 wrote

I prefer hope and dreams that if you get a little foot in the door of physics you may bust it open some day. No argument from me that there is a long way to go and propably regulariy in the wrong direction. I am however also sure that we have enough glimpses seen that einstein is not the last of it.

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