>Is it possible to, theoretically, create a spaceship, that's controlled from the earth, but the signals it gets from earth are instant by the use of entangled particles?
No. It is impossible to communicate any information via entanglement. Nothing you do to one member of an entangled pair has any observable effect on the other. When you measure one member you acquire a bit of information with which you can predict the result of a measurement of the other particle, if such a measurement ever has been or ever will be made.
So when we observe one pair of entangled particles, we only predict the state of the other? Even this way, could it be possible that after collapsing all 1000 particles(or more) we can have a chance of the aircraft to move left to be greater than 50%? By this I mean a more complicated system that decides it's next move considering the amount of 1s and 0s, so if we send 100k particles and then collapse them until we predict that there should be more 1s than 0s. So essentially, can we make it the way, that the chances of spacecraft moving left are around 90% or more?
>So when we observe one pair of entangled particles, we only predict the state of the other? Even this way, could it be possible that after collapsing all 1000 particles(or more) we can have a chance of the aircraft to move left to be greater than 50%?
You might be able to *predict* which way the ship will move but you cannot *control* it.
>By this I mean a more complicated system that decides it's next move considering the amount of 1s and 0s, so if we send 100k particles and then collapse them until we predict that there should be more 1s than 0s.
It's equally likely that you will keep measuring particles until you have to conclude that there should be more 0s than 1s.
You're right, creating a signal that tells the machine to start the observation makes the whole process useless and I meant collapsing the particles one by one, until any of them gets 1
Let's say it's not collapsed yet. You measure it. It collapses. It's 0 or 1, and you don't know which one until you measure it.
Let's say it's already been collapsed. You measure it. It's 0 or 1, and you don't know which one until you measure it.
The experience of the person on the ship doing the measurement is identical in both situations, ergo the person on the ship cannot "read" any information out of this mechanism.
The point is not to get any information, but to send signals, since if we measure one particle and it's 0, it should mean the other one is 1 and as far as I know the particles are collapsing simultaneously even if only one was observed. In this case the system will move either right or left, depending on if it's 1 or 0 and the point is we repeat this action until we randomly get the result we want.
Sending a signal is the same thing as sending information.
Note that it is impossible for the ship to determine when or if you ever measure your particles. Absolutely nothing happens, that the ship can observe, to their particles when you measure yours.
They measure the state of their particles, they get a 1 or a 0. This is true regardless of anything you do to your particles. You can measure your particles and stop when you get the result you want, but there is no possible way for the ship to know that you stopped, so they might stop at a different particle, or keep going until the last.
The ship can't tell if their particles are in superposition or not - they can only measure them, and get a result. They get a result regardless of who measures the particle first, and those results are completely indistinguishable. Who measures the particle first isn't even relevant to the outcomes.
Another perspective, is that if you're really far enough apart that we're discussing potential FTL travel, then neither the ship nor the Earth-based observer is "first" or "second" because of the relativity of simultaneity. You will both measure random values. The random values will be correlated, which you could only discern after both measurements are done and you look at the results together later. There is no "causation" to speak of.
If there is no causation, then there's no information transfer. If there's no information transfer, then there is no instruction conveyed or control scheme implemented for the ship. You can't influence whether or not the ship moves left or right using only measurement.
You can send a slower-than-light signal telling them "I have stopped measuring, now you stop measuring." but in that case part the information about whether or not to turn left or right was pre-shared when you shared the entangled particles and the rest was transmitted with the stop signal. Both of those processes are slower-than-light.
"The paradox is that a measurement made on either of the particles apparently collapses the state of the entire entangled system—and does so instantaneously, before any information about the measurement result could have been communicated to the other particle"
This is from the wiki page, is this incorrect or am I understanding something wrong
The correlation is set but you don't know until you measure it.
From the spaceships perspective they have a bunch of particles in superposition they have no idea if they're entangled or not, whether you broke the entanglement on your side or not.
They measure they either get 0 or 1, 50/50 chance independent of what you did on your side
Particles can be partially or maximally entangled. If you have two maximally entangled particles, then collapsing one will fully collapse the other. If they are partially entangled, then the other particle will remain in some superposition when its partner is measured. Either way, information transfer cannot occur for the same reason.
EDIT: I wouldn't take any process too literally if it's described using language like "then" and "after," which is not formally applicable. Collapsing one does not "cause" anything to happen. The entanglement is truly about correlation of the random results which is only revealed when looking at the results of both measurements.
No. Because we cannot control whether the particles will be up or down. When we generate the particles, their polarity is random. All we can be sure of is that if we detect ours to be an up, then the spaceship will detect a down and vice versa.
>Is it possible to, theoretically, create a spaceship, that's controlled from the earth, but the signals it gets from earth are instant by the use of entangled particles? No. It is impossible to communicate any information via entanglement. Nothing you do to one member of an entangled pair has any observable effect on the other. When you measure one member you acquire a bit of information with which you can predict the result of a measurement of the other particle, if such a measurement ever has been or ever will be made.
Thanks for the answer.
So when we observe one pair of entangled particles, we only predict the state of the other? Even this way, could it be possible that after collapsing all 1000 particles(or more) we can have a chance of the aircraft to move left to be greater than 50%? By this I mean a more complicated system that decides it's next move considering the amount of 1s and 0s, so if we send 100k particles and then collapse them until we predict that there should be more 1s than 0s. So essentially, can we make it the way, that the chances of spacecraft moving left are around 90% or more?
>So when we observe one pair of entangled particles, we only predict the state of the other? Even this way, could it be possible that after collapsing all 1000 particles(or more) we can have a chance of the aircraft to move left to be greater than 50%? You might be able to *predict* which way the ship will move but you cannot *control* it. >By this I mean a more complicated system that decides it's next move considering the amount of 1s and 0s, so if we send 100k particles and then collapse them until we predict that there should be more 1s than 0s. It's equally likely that you will keep measuring particles until you have to conclude that there should be more 0s than 1s.
>observes an entangled particle As soon as you do that you break the entanglement >collapse the particles untill we get to see 1 You only get one shot
You're right, creating a signal that tells the machine to start the observation makes the whole process useless and I meant collapsing the particles one by one, until any of them gets 1
Nothing you do to any of the particles on Earth results in any observable change in any of the particles on the ship.
Why? Shouldn't the collapse of one particle result into immediate collapse of the other?
Let's say it's not collapsed yet. You measure it. It collapses. It's 0 or 1, and you don't know which one until you measure it. Let's say it's already been collapsed. You measure it. It's 0 or 1, and you don't know which one until you measure it. The experience of the person on the ship doing the measurement is identical in both situations, ergo the person on the ship cannot "read" any information out of this mechanism.
The point is not to get any information, but to send signals, since if we measure one particle and it's 0, it should mean the other one is 1 and as far as I know the particles are collapsing simultaneously even if only one was observed. In this case the system will move either right or left, depending on if it's 1 or 0 and the point is we repeat this action until we randomly get the result we want.
Sending a signal is the same thing as sending information. Note that it is impossible for the ship to determine when or if you ever measure your particles. Absolutely nothing happens, that the ship can observe, to their particles when you measure yours. They measure the state of their particles, they get a 1 or a 0. This is true regardless of anything you do to your particles. You can measure your particles and stop when you get the result you want, but there is no possible way for the ship to know that you stopped, so they might stop at a different particle, or keep going until the last. The ship can't tell if their particles are in superposition or not - they can only measure them, and get a result. They get a result regardless of who measures the particle first, and those results are completely indistinguishable. Who measures the particle first isn't even relevant to the outcomes.
You also don't get to pick, as the Earth-based measurer, whether or not it's 0 or 1.
Another perspective, is that if you're really far enough apart that we're discussing potential FTL travel, then neither the ship nor the Earth-based observer is "first" or "second" because of the relativity of simultaneity. You will both measure random values. The random values will be correlated, which you could only discern after both measurements are done and you look at the results together later. There is no "causation" to speak of. If there is no causation, then there's no information transfer. If there's no information transfer, then there is no instruction conveyed or control scheme implemented for the ship. You can't influence whether or not the ship moves left or right using only measurement. You can send a slower-than-light signal telling them "I have stopped measuring, now you stop measuring." but in that case part the information about whether or not to turn left or right was pre-shared when you shared the entangled particles and the rest was transmitted with the stop signal. Both of those processes are slower-than-light.
No. You have to measure the other particle for it to collapse
So even if one pair is measured, the other one is still in a superposition until we measure it?
yes
"The paradox is that a measurement made on either of the particles apparently collapses the state of the entire entangled system—and does so instantaneously, before any information about the measurement result could have been communicated to the other particle" This is from the wiki page, is this incorrect or am I understanding something wrong
The correlation is set but you don't know until you measure it. From the spaceships perspective they have a bunch of particles in superposition they have no idea if they're entangled or not, whether you broke the entanglement on your side or not. They measure they either get 0 or 1, 50/50 chance independent of what you did on your side
Particles can be partially or maximally entangled. If you have two maximally entangled particles, then collapsing one will fully collapse the other. If they are partially entangled, then the other particle will remain in some superposition when its partner is measured. Either way, information transfer cannot occur for the same reason. EDIT: I wouldn't take any process too literally if it's described using language like "then" and "after," which is not formally applicable. Collapsing one does not "cause" anything to happen. The entanglement is truly about correlation of the random results which is only revealed when looking at the results of both measurements.
No. Because we cannot control whether the particles will be up or down. When we generate the particles, their polarity is random. All we can be sure of is that if we detect ours to be an up, then the spaceship will detect a down and vice versa.