NIST Physicists Show Ion Pairs Perform Enhanced 'Spooky Action'
1–10 of 59 posts
Re: NIST Physicists Show Ion Pairs Perform Enhanced 'Spooky Action'
#2One 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.
Re: NIST Physicists Show Ion Pairs Perform Enhanced 'Spooky Action'
#3One 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 t…
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.
Re: NIST Physicists Show Ion Pairs Perform Enhanced 'Spooky Action'
#4> “We are confident that the ions are 67 percent spooky,” said Ting Rei Tan, lead author
I love modern physics for lines like this.
Re: NIST Physicists Show Ion Pairs Perform Enhanced 'Spooky Action'
#5One 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 t…
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.
Re: NIST Physicists Show Ion Pairs Perform Enhanced 'Spooky Action'
#6susskind 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"
Re: NIST Physicists Show Ion Pairs Perform Enhanced 'Spooky Action'
#7One 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 t…
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…
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
Re: NIST Physicists Show Ion Pairs Perform Enhanced 'Spooky Action'
#8One 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 t…
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…
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.
Re: NIST Physicists Show Ion Pairs Perform Enhanced 'Spooky Action'
#9susskind 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 whet…
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.
Re: NIST Physicists Show Ion Pairs Perform Enhanced 'Spooky Action'
#10susskind 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 whet…
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 b…
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