7 ms·

NIST Physicists Show Ion Pairs Perform Enhanced 'Spooky Action'

59 points by sconxu 10y ago

headcanon 10y ago
One think I've been wondering about spooky action is if entanglement reactions are bound to the speed of light. As in, if one particle of the entangled pair is manipulated, is there a "signal" that is "transmitted" at some speed? Or is it "instant" in the sense that it transcends lightspeed? Or does this question even make sense in this context? Quantum stuff gets weird fast since we have very little basis in which to intuit it.
- danbruc 10y ago
  It is instantly but you can not use it to transmit information. Say you have a pair of entangled spins in a superposition of the two anti-parallel states first spin up and second spin down or first spin down and second spin up with equal probability for both states, i.e. each spin is up or down with a probability of 50 % but the two spins always have opposing orientations. If you measure one of the spins, then there is no time, no matter how far the spins are separated, in which you could measure the second spin to have the same orientation as the one you just measured because the result of the measurement somehow had not yet enough time to reached the second spin, supposedly because this state change is limited to travel at the speed of light. It is as if the spins had secretly picked on of the two possible outcomes when they were created but you just do not know which one until you perform a measurement. But this is not the case, this is what is called a local hidden variable theory and is ruled out by Bell test experiments. The spins have no definite orientation until you measure the first one but after the first measurement both spins instantaneously have a definit orientation no matter how far separated.
  - platz 10y ago
    a side note, there isn't a universal "spin orientation detector" that reveals a spin orientation on the unit circle. You have to choose how to align the magnets so that the spin measured is either "up" or "down"; you could align the magnets any way you like, but they are fixed along an axis for the duration of the observation
  - tedsanders 10y ago
    There is no proof or strong evidence that this occurs instantly. Some interpretations of quantum mechanics still satisfy locality. https://en.m.wikipedia.org/wiki/Interpretations_of_quantum_mechanics https://en.m.wikipedia.org/wiki/Interpretations_of_quantum_m...
    - danbruc 10y ago
      One has to be careful what one means here. I meant it in the following specific sense and we have good experimental evidence for this. [...] there is no time, no matter how far the spins are separated, in which you could measure the second spin to have the same orientation as the one you just measured [...] If an interpretation makes use of non-locality to explain this fact is a different matter, but experimentally it looks exactly like measurements instantaneously affecting entangled partners.
      - deleted 10y ago
        [deleted]
- btilly 10y ago
  The idea works like this. A pair of particles is entangled then separated to positions L and L'. At L we can observe A or B. At L' we can observe A' or B'. Until the moment of observation, it is indeterminate which. L and L' are too far apart and close in time for information to be communicated by light. The point of the EPR experiment is that when we observe A at L we will observe A' at L'. And when we observe B at L we will observe B at B'. In other words "collapse is instantaneous". In the many worlds interpretation, nothing is actually happening faster than light. At L we split into an A and a B observer. At L' we split into an A' and a B' observer. And then when those observers meet up, QM just describes how those observers match up to generate two consistent stories. However this is a very, very important for theoretical physics. General Relativity is an inherently local theory. QM is inherently nonlocal. In decades of trying, nobody has figured out how to come up with a theory that bridges them.
  - danbruc 10y ago
    General Relativity is an inherently local theory. QM is inherently nonlocal. In decades of trying, nobody has figured out how to come up with a theory that bridges them. But to add, there are at least ideas, it is not the case that we made no progress at all. I would like to highlight the ER=EPR conjecture [1] by Leonard Susskind and Juan Maldacena. It roughly states that entangled particles are connected by worm holes and that they are therefore not actually separated in space. Personally I prefer a less sensationalist sounding description, that entanglement defines what it means for points in space to be close together or far apart. This avoids constantly visualizing pairs of particle connected by glowing worm holes from science fiction movies. [1] https://en.wikipedia.org/wiki/ER%3DEPR https://en.wikipedia.org/wiki/ER%3DEPR
    - intrasight 10y ago
      You don't need a wormhole, as there are no particles, and therefore nothing is "separated".
      - danbruc 10y ago
        I have no idea what you mean, there are obviously particles, we have an entire standard model full of them.
- cgc0 10y ago
  Although I'll certainly butcher the phrasing, my understanding is: measuring a property of one of the entangled particles lets you know the same property of the other particle (an experiment showed this happens faster than the speed of light by measuring the two particles when they were 1.3km apart). This is particularly mysterious because it seems that the property of the particle is not determined before this measurement. Here are some quotes from a piece on the experiment I mentioned above. from https://www.sciencenews.org/blog/context/entanglement-spooky-not-action-distance https://www.sciencenews.org/blog/context/entanglement-spooky... > Einstein insisted that the handedness of the glove must be determined in advance by some physical law. He was perplexed by the possibility that Alice’s choice of hand could have something to do with whether Bob’s glove would fit his fingers. > Suppose you prepared entangled photons and sent them to Alice and Bob in such a way that if Alice measured hers to be vertically polarized, she instantly knows that Bob’s will be horizontally polarized. . . . > . . . The photon does not have an orientation until Alice detects it. Same for Bob’s. But once Alice makes a measurement, the outcome of Bob’s measurement is certain. > Here’s where a lot of confusion clouds entanglement commentary. Contrary to what you might have read in a magazine with “New” and “Yorker” in the title, Alice’s measurement does not “instantaneously” influence Bob’s photon. No signal is sent, no influence transmitted. For all Alice knows, Bob might have measured his photon first. In fact, if the measurements are made at nearly the same time, there might be no objective way to say who made the first measurement. (A space traveler flying along at nearly the speed of light might see Bob’s measurement first, while another traveler flying in a different direction would see Alice’s first.)
- return0 10y ago
  They are not bound by speed of light. Nothing is exchanged or transmitted, the collapse of wavefunction is genuinely instant in both places. The drawback is that you cannot choose or predict which outcome you will measure, so you can't really use it to transmit information instantly.
mabbo 10y ago
> “We are confident that the ions are 67 percent spooky,” said Ting Rei Tan, lead author I love modern physics for lines like this.
- komali2 10y ago
  I wonder if they were an even spookier 66.6...% spooky, but Ting Rei Tan didn't want to say that cause that'd just be 2spoopy4me
platz 10y ago
susskind described entanglement in a bit different way than I'd heard - "that entanglement allows one to know everything there is to know about a system of particles (the whole), while knowing nothing about it's parts." In the classical version of an information experiment, if i randomize placement of objects A and B into 2 boxes, and send one of those boxes to someone else - upon opening my box I instantly know whether the other box contains object A or B. The Quantum Mechanical version of the above experiment is very similar, except there could be several different degreees of freedom to measure on upon opening my box (what angle of spin measure on, etc..) So to me, that doesn't suggest that something "traveled" to the other box, just like in the Classical version. Rather, somehow I only "knew" the system at the beginning without knowing "any of it's parts" (due to entanglement & superposition). Then, just observing a degree of freedom in one the parts finally reveals what the corresponding degree of freedom in the other part was. This (intuitively) makes more sense to me than saying "information traveled" and "action at a distance"
- equivrel 10y ago
  The objects in boxes scenario you have described is useful to think about when coming to grips with QM and entanglement. However, one needs to be careful, because there is an additional subtlety: QM can have measurement scenarios that are not only entangled, but also non-local [1]. This means that it is provably impossible to endow the variables that you are measuring with prior, local assignments, e.g. like in the boxes scenario. So there is actually another phenomenon present in QM that makes it weird, and is strictly speaking distinct from entanglement. [1] - https://en.wikipedia.org/wiki/Quantum_nonlocality https://en.wikipedia.org/wiki/Quantum_nonlocality
  - platz 10y ago
    locality is looking suspect for other reasons too, as it's one of the only ways to avoid 'black hole firewalls' [1] (the other way to avoid firewalls involves giving up conservation of information which would be bad for QM theory). [1] Black hole Firewalls with Sean Carroll and Jennifer Ouellette https://www.youtube.com/watch?v=_8bhtEgB8Mo&t=3634s https://www.youtube.com/watch?v=_8bhtEgB8Mo&t=3634s
nonbel 10y ago
Why does this not describe the "entanglement" phenomenon: 1) Alice, Bob, and Charlie are in a room. 2) Alice has only an apple and a pear, seen by Charlie. 3) Charlie leaves the room. 4) Alice gives one of the two fruits to Bob. 5) Bob leaves the room to meet up with Charlie and starts eating the pear. 6) Charlie instantly knows that Alice has the apple, no matter where she has ended up in the universe (which is not spooky at all).
- danbruc 10y ago
  Because Bob leaves the room with either an apple or a pear and this choice is made inside the room. In quantum physics Bob would leave the room with half an apple and half a pear, Charlie would ask Bob to eat the pear, and in this moment Bob's half of the apple would teleport to Alice and Alice's half of the pear to Bob. Charlie could also have asked Bob to eat the apple. Very roughly speaking, this picture is actually flawed. Charlie can not choose the fruit to eat in quantum mechanics. In this picture you would also transmit Charlie's choice to Alice faster than the speed of light which is not possible in quantum mechanics. The important part of this picture is that Bob does not leave the room with a predetermined fruit, the choice happens later outside of the room but Alice still always ends up with the other fruit, Alice and Bob never end up with the same fruit.
  - mirimir 10y ago
    I get how "teleport" isn't QM. But the issue for both is locality violation.
  - nonbel 10y ago
    Thanks, > "Charlie would ask Bob to eat the pear" This seems to be the key part. So when they run experiments on this, a certain result can be forced? > "The important part is that Bob does not leave the room with predetermined fruit." Right, is this aspect measured somehow or only inferred from the theory?
    - danbruc 10y ago
      I tried to set this straight in my comment. Charlie does not get to choose the fruit, the fruit is chosen at random. I just allowed Charlie to make the choice to emphasize that the choice happens outside of the room. Had I just said the choice happens at random, then it would not be obvious why this random choice could not also be made in the room with Alice. But then we were back at Bob leaving the room with either an apple or a pear. Have I look at my other comment with coins in boxes [1], that picture captures the situation better and in a way that is not easily translated to fruits. [1] https://news.ycombinator.com/item?id=13981054 https://news.ycombinator.com/item?id=13981054
Balgair 10y ago
Oh cool! This experiment is very fun, not just from the results side. I was able to get a tour with the photonic side of this set-up (not the atomic side, as this paper elucidates). The photons are made entangled, then split and sent into some fiber-optic cables that run about in the tracts in the hallways. The rooms used to measure the entanglements are sufficiently far apart, but due to budgets, are at right angles from the source. We only went to one of the rooms, but the measurement devices are housed in marijuana grow pods you can buy, as they tend to keep the temperature stable, have access for the wires and cryogenic tubes, will keep out/in EM noise, and are pretty cheap. There was a line on the floor of that room, off in the corner, that had where the 'light speed' signal from the other measurement room stopped when the measurement (in the room we were in) was made, proving that the measurements could not interact. If you ever get a chance, get a tour at NIST, it is well worth whatever strings you have to pull. Getting to see The United States Second (where the US measures all of out time from) was a real highlight of my scientific career.
chakalakasp 10y ago
One of the more head exploding experiments I've seen regarding entanglement is this one: https://youtu.be/u9bXolOFAB8 https://youtu.be/u9bXolOFAB8 By all apparences, it seems to violate causality. It's one of those things that make you suddenly stop and bemusedly wonder if maybe we've finally found a kludge in the Universe's code. edit BTW, if you'd like to know more about this experiment and why it has ridiculous implications, check this PBS clip: https://youtu.be/8ORLN_KwAgs https://youtu.be/8ORLN_KwAgs

59 points by sconxu 10y ago

One think I've been wondering about spooky action is if entanglement reactions are bound to the speed of light. As in, if one particle of the entangled pair is manipulated, is there a "signal" that is "transmitted" at some speed? Or is it "instant" in the sense that it transcends lightspeed? Or does this question even make sense in this context? Quantum stuff gets weird fast since we have very little basis in which to intuit it.

danbruc 10y ago
It is instantly but you can not use it to transmit information. Say you have a pair of entangled spins in a superposition of the two anti-parallel states first spin up and second spin down or first spin down and second spin up with equal probability for both states, i.e. each spin is up or down with a probability of 50 % but the two spins always have opposing orientations. If you measure one of the spins, then there is no time, no matter how far the spins are separated, in which you could measure the second spin to have the same orientation as the one you just measured because the result of the measurement somehow had not yet enough time to reached the second spin, supposedly because this state change is limited to travel at the speed of light. It is as if the spins had secretly picked on of the two possible outcomes when they were created but you just do not know which one until you perform a measurement. But this is not the case, this is what is called a local hidden variable theory and is ruled out by Bell test experiments. The spins have no definite orientation until you measure the first one but after the first measurement both spins instantaneously have a definit orientation no matter how far separated.
- platz 10y ago
  a side note, there isn't a universal "spin orientation detector" that reveals a spin orientation on the unit circle. You have to choose how to align the magnets so that the spin measured is either "up" or "down"; you could align the magnets any way you like, but they are fixed along an axis for the duration of the observation
- tedsanders 10y ago
  There is no proof or strong evidence that this occurs instantly. Some interpretations of quantum mechanics still satisfy locality. https://en.m.wikipedia.org/wiki/Interpretations_of_quantum_mechanics https://en.m.wikipedia.org/wiki/Interpretations_of_quantum_m...
  - danbruc 10y ago
    One has to be careful what one means here. I meant it in the following specific sense and we have good experimental evidence for this. [...] there is no time, no matter how far the spins are separated, in which you could measure the second spin to have the same orientation as the one you just measured [...] If an interpretation makes use of non-locality to explain this fact is a different matter, but experimentally it looks exactly like measurements instantaneously affecting entangled partners.
    - deleted 10y ago
      [deleted]
btilly 10y ago
The idea works like this. A pair of particles is entangled then separated to positions L and L'. At L we can observe A or B. At L' we can observe A' or B'. Until the moment of observation, it is indeterminate which. L and L' are too far apart and close in time for information to be communicated by light. The point of the EPR experiment is that when we observe A at L we will observe A' at L'. And when we observe B at L we will observe B at B'. In other words "collapse is instantaneous". In the many worlds interpretation, nothing is actually happening faster than light. At L we split into an A and a B observer. At L' we split into an A' and a B' observer. And then when those observers meet up, QM just describes how those observers match up to generate two consistent stories. However this is a very, very important for theoretical physics. General Relativity is an inherently local theory. QM is inherently nonlocal. In decades of trying, nobody has figured out how to come up with a theory that bridges them.
- danbruc 10y ago
  General Relativity is an inherently local theory. QM is inherently nonlocal. In decades of trying, nobody has figured out how to come up with a theory that bridges them. But to add, there are at least ideas, it is not the case that we made no progress at all. I would like to highlight the ER=EPR conjecture [1] by Leonard Susskind and Juan Maldacena. It roughly states that entangled particles are connected by worm holes and that they are therefore not actually separated in space. Personally I prefer a less sensationalist sounding description, that entanglement defines what it means for points in space to be close together or far apart. This avoids constantly visualizing pairs of particle connected by glowing worm holes from science fiction movies. [1] https://en.wikipedia.org/wiki/ER%3DEPR https://en.wikipedia.org/wiki/ER%3DEPR
  - intrasight 10y ago
    You don't need a wormhole, as there are no particles, and therefore nothing is "separated".
    - danbruc 10y ago
      I have no idea what you mean, there are obviously particles, we have an entire standard model full of them.
cgc0 10y ago
Although I'll certainly butcher the phrasing, my understanding is: measuring a property of one of the entangled particles lets you know the same property of the other particle (an experiment showed this happens faster than the speed of light by measuring the two particles when they were 1.3km apart). This is particularly mysterious because it seems that the property of the particle is not determined before this measurement. Here are some quotes from a piece on the experiment I mentioned above. from https://www.sciencenews.org/blog/context/entanglement-spooky-not-action-distance https://www.sciencenews.org/blog/context/entanglement-spooky... > Einstein insisted that the handedness of the glove must be determined in advance by some physical law. He was perplexed by the possibility that Alice’s choice of hand could have something to do with whether Bob’s glove would fit his fingers. > Suppose you prepared entangled photons and sent them to Alice and Bob in such a way that if Alice measured hers to be vertically polarized, she instantly knows that Bob’s will be horizontally polarized. . . . > . . . The photon does not have an orientation until Alice detects it. Same for Bob’s. But once Alice makes a measurement, the outcome of Bob’s measurement is certain. > Here’s where a lot of confusion clouds entanglement commentary. Contrary to what you might have read in a magazine with “New” and “Yorker” in the title, Alice’s measurement does not “instantaneously” influence Bob’s photon. No signal is sent, no influence transmitted. For all Alice knows, Bob might have measured his photon first. In fact, if the measurements are made at nearly the same time, there might be no objective way to say who made the first measurement. (A space traveler flying along at nearly the speed of light might see Bob’s measurement first, while another traveler flying in a different direction would see Alice’s first.)
return0 10y ago
They are not bound by speed of light. Nothing is exchanged or transmitted, the collapse of wavefunction is genuinely instant in both places. The drawback is that you cannot choose or predict which outcome you will measure, so you can't really use it to transmit information instantly.

mabbo 10y ago

> “We are confident that the ions are 67 percent spooky,” said Ting Rei Tan, lead author I love modern physics for lines like this.

komali2 10y ago
I wonder if they were an even spookier 66.6...% spooky, but Ting Rei Tan didn't want to say that cause that'd just be 2spoopy4me

platz 10y ago

susskind described entanglement in a bit different way than I'd heard - "that entanglement allows one to know everything there is to know about a system of particles (the whole), while knowing nothing about it's parts." In the classical version of an information experiment, if i randomize placement of objects A and B into 2 boxes, and send one of those boxes to someone else - upon opening my box I instantly know whether the other box contains object A or B. The Quantum Mechanical version of the above experiment is very similar, except there could be several different degreees of freedom to measure on upon opening my box (what angle of spin measure on, etc..) So to me, that doesn't suggest that something "traveled" to the other box, just like in the Classical version. Rather, somehow I only "knew" the system at the beginning without knowing "any of it's parts" (due to entanglement & superposition). Then, just observing a degree of freedom in one the parts finally reveals what the corresponding degree of freedom in the other part was. This (intuitively) makes more sense to me than saying "information traveled" and "action at a distance"

equivrel 10y ago
The objects in boxes scenario you have described is useful to think about when coming to grips with QM and entanglement. However, one needs to be careful, because there is an additional subtlety: QM can have measurement scenarios that are not only entangled, but also non-local [1]. This means that it is provably impossible to endow the variables that you are measuring with prior, local assignments, e.g. like in the boxes scenario. So there is actually another phenomenon present in QM that makes it weird, and is strictly speaking distinct from entanglement. [1] - https://en.wikipedia.org/wiki/Quantum_nonlocality https://en.wikipedia.org/wiki/Quantum_nonlocality
- platz 10y ago
  locality is looking suspect for other reasons too, as it's one of the only ways to avoid 'black hole firewalls' [1] (the other way to avoid firewalls involves giving up conservation of information which would be bad for QM theory). [1] Black hole Firewalls with Sean Carroll and Jennifer Ouellette https://www.youtube.com/watch?v=_8bhtEgB8Mo&t=3634s https://www.youtube.com/watch?v=_8bhtEgB8Mo&t=3634s

nonbel 10y ago

Why does this not describe the "entanglement" phenomenon: 1) Alice, Bob, and Charlie are in a room. 2) Alice has only an apple and a pear, seen by Charlie. 3) Charlie leaves the room. 4) Alice gives one of the two fruits to Bob. 5) Bob leaves the room to meet up with Charlie and starts eating the pear. 6) Charlie instantly knows that Alice has the apple, no matter where she has ended up in the universe (which is not spooky at all).

danbruc 10y ago
Because Bob leaves the room with either an apple or a pear and this choice is made inside the room. In quantum physics Bob would leave the room with half an apple and half a pear, Charlie would ask Bob to eat the pear, and in this moment Bob's half of the apple would teleport to Alice and Alice's half of the pear to Bob. Charlie could also have asked Bob to eat the apple. Very roughly speaking, this picture is actually flawed. Charlie can not choose the fruit to eat in quantum mechanics. In this picture you would also transmit Charlie's choice to Alice faster than the speed of light which is not possible in quantum mechanics. The important part of this picture is that Bob does not leave the room with a predetermined fruit, the choice happens later outside of the room but Alice still always ends up with the other fruit, Alice and Bob never end up with the same fruit.
- mirimir 10y ago
  I get how "teleport" isn't QM. But the issue for both is locality violation.
- nonbel 10y ago
  Thanks, > "Charlie would ask Bob to eat the pear" This seems to be the key part. So when they run experiments on this, a certain result can be forced? > "The important part is that Bob does not leave the room with predetermined fruit." Right, is this aspect measured somehow or only inferred from the theory?
  - danbruc 10y ago
    I tried to set this straight in my comment. Charlie does not get to choose the fruit, the fruit is chosen at random. I just allowed Charlie to make the choice to emphasize that the choice happens outside of the room. Had I just said the choice happens at random, then it would not be obvious why this random choice could not also be made in the room with Alice. But then we were back at Bob leaving the room with either an apple or a pear. Have I look at my other comment with coins in boxes [1], that picture captures the situation better and in a way that is not easily translated to fruits. [1] https://news.ycombinator.com/item?id=13981054 https://news.ycombinator.com/item?id=13981054

Balgair 10y ago

Oh cool! This experiment is very fun, not just from the results side. I was able to get a tour with the photonic side of this set-up (not the atomic side, as this paper elucidates). The photons are made entangled, then split and sent into some fiber-optic cables that run about in the tracts in the hallways. The rooms used to measure the entanglements are sufficiently far apart, but due to budgets, are at right angles from the source. We only went to one of the rooms, but the measurement devices are housed in marijuana grow pods you can buy, as they tend to keep the temperature stable, have access for the wires and cryogenic tubes, will keep out/in EM noise, and are pretty cheap. There was a line on the floor of that room, off in the corner, that had where the 'light speed' signal from the other measurement room stopped when the measurement (in the room we were in) was made, proving that the measurements could not interact. If you ever get a chance, get a tour at NIST, it is well worth whatever strings you have to pull. Getting to see The United States Second (where the US measures all of out time from) was a real highlight of my scientific career.

chakalakasp 10y ago

One of the more head exploding experiments I've seen regarding entanglement is this one: https://youtu.be/u9bXolOFAB8 https://youtu.be/u9bXolOFAB8 By all apparences, it seems to violate causality. It's one of those things that make you suddenly stop and bemusedly wonder if maybe we've finally found a kludge in the Universe's code. edit BTW, if you'd like to know more about this experiment and why it has ridiculous implications, check this PBS clip: https://youtu.be/8ORLN_KwAgs https://youtu.be/8ORLN_KwAgs

NIST Physicists Show Ion Pairs Perform Enhanced &#039;Spooky Action&#039;

NIST Physicists Show Ion Pairs Perform Enhanced &#039;Spooky Action&#039;

NIST Physicists Show Ion Pairs Perform Enhanced 'Spooky Action'

NIST Physicists Show Ion Pairs Perform Enhanced 'Spooky Action'