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StuckinbedtilDec t1_ispzr5j wrote

Is this the quantum entanglement that relays information instantaneously across any distance?

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matpompili OP t1_isq0qyp wrote

Hi! The quantum entanglement itself does happen instantaneously, but it cannot be used to send messages faster than the speed of light. A good analogy is the following, from John Bell:

«The situation is further complicated by the fact that there are things which do go faster than light. British sovereignty is the classical example. When the Queen dies in London (may it long be delayed) the Prince of Wales, lecturing on modern architecture in Australia, becomes instan taneously King.»

So the entanglement effect is instantaneous, like the transfer of sovereignty, but until the information reaches the other side it is not known. So you cannot use entanglement to communicate faster than the speed of light.

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StuckinbedtilDec t1_isq1qn3 wrote

Someone's been bullshitting people for years into believing that quantum entangled particles would change their combined spin instantly across any distance.

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matpompili OP t1_isq2kpe wrote

LOL, they do go into one of their joint possible states instantly across any distance! The "issue" is that you cannot extract any faster-than-light messaging technology from this.

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SomeoneSomewhere1984 t1_isqab2c wrote

I think we just don't know how to use if for that yet, but think we'll figure out a way at some point in the distant future.

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Specialist-Doctor-23 t1_isqf0oq wrote

Of course we could. One only needs the remote means to detect, in real time, any of the states of the remote particle and the ability to control the same state of its twin. Of course, this only confers an advantage when the distance (and therefore the time required for a light-speed message) between pairs exceeds the response time of such quantum state message system.

Oh! And some way to establish and sustain control and observation of entangled pairs😏

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Exodus111 t1_isreqlt wrote

It could likely be used for interstellar communication.

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runswithcoyotes t1_isrt18g wrote

Why not? Any change is itself a message.

Edit: to whoever downvoted me, you obviously don’t understand signaling. Any change in states, is at the very least a binary message. Couple that with timing, and multiple bits, and you’ve got yourself a full-fledged messaging platform. Egg heads like OP here aren’t able to explain why this wont work. I’m happy to listen to an explanation, if one could just be provided.

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runswithcoyotes t1_it4yed7 wrote

Ah, thanks! So I this explains why you can’t send specific values:

If you force one side to change, it breaks the entanglement. UNLESS you modify the state in a way that you can compare the changes that led to the state later. I don’t really understand why that is, and will need to dig into the nested links to find out.

> Alice and Bob end up with measurements that are perfectly correlated, no information passes between them. They can only see the correlation when they get back together and compare lists, and they have to do that at or below the speed of light.

But! My question wasn’t actually about specific states, it was about changes in states. Which.. to me still seems possible.

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SuperSpread t1_isqmtqe wrote

It’s the same fallacy as saying a shadow travels faster than the speed of light when you turn a light on. The shadow was already there. With entangled particles you are merely resolving information.

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Powerful_Range_4270 t1_isrybaj wrote

I think the common phrase of "anything is possible with Quantum physics" is what's causing this.

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crumbshotfetishist t1_isre0mk wrote

Wow. I have never felt so close to feeling like I might actually have some grasp of what quantum entanglement actually means.

What are the limits to the analogy drawn here between this ‘sovereign entanglement’ and quantum entanglement? In other words, what can and can’t Bell’s example help explain about quantum entanglement?

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Suttonian t1_isq04t5 wrote

As far as I'm aware, that is not thought to be possible - no information can be transmitted faster than light.

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StuckinbedtilDec t1_isq18m7 wrote

Bell tests have been performed where the locations were sufficiently separated that communications at the speed of light would have taken longer—in one case, 10,000 times longer—than the interval between the measurements.[7][6]

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

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matpompili OP t1_isq1p6z wrote

Yes, entanglement and its effect propagate instantaneously, but that cannot be used to send information faster than the speed of light.

Check out this video from Veritasium, it explains very nicely why that is the case: https://www.youtube.com/watch?v=ZuvK-od647c

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StuckinbedtilDec t1_isq4it1 wrote

As long as the effect can be detected then information could be sent.

Left spin = zero

Right spin = one

Time to go binary... 01101000101011... all over again.

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matpompili OP t1_isq5v6a wrote

The problem with your argument is that you cannot force the system to go "left" or "right".
All that entanglement gives you is: either the two spins go "left-right", or they go "right-left", but you cannot force the system in one of the two options.
So when you measure your spin, and you get "left", you know that the other spin will be right, but you have no way to imprint a message on this process.
You can only use this as a correlated source of random events (which is why it is so useful for cryptography)

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StuckinbedtilDec t1_isq6vwf wrote

Won't the other particle be effected (in a detectable way) when the first one is measured?

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matpompili OP t1_isq7f52 wrote

Without communication between the two sides, no: imagine you are in a closed room, no communication to the outside, and have one of the spins.
You measure it repeatedly, and you get random outcomes: 0, 1, 1, 0, 0.
The other side got 1, 0, 0, 1, 1, but since neither you nor the other side has a way to change what those bits are going to be, all you have after measuring is a correlated list of random numbers.
The fundamental problem, is that you have no way to tell whether the other side has done anything to their spin. If the other side had not done anything, you could have totally gotten the same string of random bits!

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StuckinbedtilDec t1_isq96ja wrote

Would the other side know exactly when the measurement was being conducted?

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matpompili OP t1_isqbrmy wrote

They could, it would not change the result. The measurement of the two spins gives correlated results, it does not change the result.

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StuckinbedtilDec t1_isqc9ia wrote

Then it is possible to send information by knowing exactly when the measurement was being conducted. As long as both groups have clocks that are synchronized then a 1/0 could be transferred based on the timing of the measurement.

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Suttonian t1_isqdtu3 wrote

Let's do the experiment.

  • Team A and Team B.
  • They agree that at exactly 10 am they will take measurements.
  • Team A gets a left spin, they know Team B has the opposite.
  • Team B gets a right spin, they know Team A has the opposite.

But what information has actually been transmitted? How could a message be transmitted?

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StuckinbedtilDec t1_isqgegx wrote

If team A takes a secret measurement at 10 am there's no way team B would know what time it was taken?

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Suttonian t1_isqryyy wrote

No there is no way for them to know if team A took a secret measurement.

If either side measures the entangled particle it will break the entanglement, the 'connection' is lost.

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StuckinbedtilDec t1_isqsxdp wrote

Could B team detect the moment a connection was lost?

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Suttonian t1_isqzspi wrote

No. Any detection/measurement results in the entanglement breaking.

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warplants t1_isr24mq wrote

No. The only possible way to know there was a connection in the first place is to compare the measurements of A and B teams; if their measurements are strongly correlated, there was a connection.

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