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…
It would be spooky if, in the middle of step 5, Malory exchanged Alice's apple for a banana. And Charlie knew that. Edit: I like danbruc's answer better.
NIST Physicists Show Ion Pairs Perform Enhanced 'Spooky Action'
31–40 of 59 posts
Re: NIST Physicists Show Ion Pairs Perform Enhanced 'Spooky Action'
#32Earlier quoted context omitted.
It would be spooky if, in the middle of step 5, Malory exchanged Alice's apple for a banana. And Charlie knew that. Edit: I like danbruc's answer better.
If that happens, the entanglement would be broken, and Charlie wouldn't know.
Re: NIST Physicists Show Ion Pairs Perform Enhanced 'Spooky Action'
#33Earlier quoted context omitted.
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…
I'm not sure your description of the difference between classical and quantum contradicts what I said. In fact I think they are compatible I didn't use any notion of "predetermination" when describing the quantum mechanical version. I said that "there could be several different degrees of freedom to measure on" I meant this to exactly correspond to "the exact outcome is only established when one looks in the first bo…
This (intuitively) makes more sense to me than saying "information traveled" and "action at a distance"
You can not get away from non-locality in quantum mechanics. Because the outcome is only determined when a measurement is performed, this »information« has to travel to the entangled partner when the measurement is made. And this must happen instantaneously. In the classical example you can avoid this because the outcome is already determined during the setup.
I said that "there could be several different degrees of freedom to measure on" I meant this to exactly correspond to "the exact outcome is only established when one looks in the first box".
This are three different things. You can of course decide to measure the spin along any axis you like, that is you can choose the observable. When you do this, then you are not measuring different degrees of freedom, you are measuring the same degree of freedom, the spin, in different bases. But, and that is what I meant, even if you always measure the spin along the same axis, say along the positive x axis, then the spin of an electron in a superposition of spin either +1 or -1 along this axis is only determined at the time of the measurement. Before that measurement the electron had no definite spin along this axis.
Re: NIST Physicists Show Ion Pairs Perform Enhanced 'Spooky Action'
#34Earlier quoted context omitted.
It doesn't have an ontology with a current prayer of being falsifies, which is the same thing if you're interested in the science and not the popsci. Exceptions exist, hence AdS/CFT correspondence and M-Theory, but they are exceptions. Even then, all that can be said is various tools have been created with value beyond their fields, not that they're in any way falsifiable yet. At any rate, "intuitive" strikes me as a…
Yeah, that's why QM and I parted ways. I'm too committed to intuition. So it goes.
Re: NIST Physicists Show Ion Pairs Perform Enhanced 'Spooky Action'
#35Why 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…
Bell's theorem places limits on the correlations that a theory like this can explain. Here's a simple example of a Bell violation:
1) Alice and Bob get together and conspire. They can do anything they want here.
2) Alice and Bob are then taken to separate interrogation chambers, to be quizzed by separate interrogators.
3) Each interrogator randomly (and independently) chooses one of three yes-or-no questions to ask their subject. Both interrogators are working from the same list of 3 questions. Alice and Bob are asked the questions and the questions and their answers are recorded.
4) This whole process is repeated many times. When the results are tabulated, it's found that every time Alice and Bob were asked the same question, they gave the same answer. But when they were asked different questions, 75% of the time they gave different answers.
How could Alice and Bob have achieved this? Classically, they couldn't. In order to always give the same answer to the same question, they'd have to (either directly or indirectly) agree beforehand on which answer to give to which question.
Since there are three possible questions but only two possible answers to them, any strategy they pick must give the same answer to (at least) two of the three questions. Therefore, if their interrogators pick different questions there's at least a 1/3 chance they'll pick the questions with the same answer.
But with quantum entanglement, the chance of getting the same answer from both is can be only 1/4. Something weirder is going on.
(BTW, for completeness, here's how the quantum results I described can be achieved: Alice and Bob are replaced by electrons, prepared in the (entangled) singlet state. The "interrogations" are measurements of their spin (up or down) on the 0°, 120°, or 240° axes, with one of the detectors set up upside-down. This is not the way it's actually done, but it's easier to explain & see the paradox this way.)
Re: NIST Physicists Show Ion Pairs Perform Enhanced 'Spooky Action'
#36Earlier quoted context omitted.
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 actual…
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?
No, a result can't be forced. The analogy being used isn't very close. I'm going to summarize an explanation used in (IIRC) The Elegant Universe that may be helpful.
Mulder and Scully each get shipped a box that's entangled with the other's box. These boxes have three windows. You're allowed to open only one window, at which point you'll see a red or green light. These boxes further have the property that they're entangled: if Mulder and Scully open the same window, they'll see the same color.
Mulder and Scully open the same window on each box, and sure enough, they see the same color. Mulder claims that it's spooky action at a distance, Scully claims that the boxes are simply preprogrammed with a preset color pattern: one of "red, red, green", "green, red, green", "red, red, red", and so on.
Mulder thinks for a bit and devises an experiment. They now acquire a large number of these boxes, each paired with a box in the other's possession (and in such a way they can identify which of their two boxes correspond to one-another). They proceed to open doors randomly, recording the results. Now they compare notes.
In the case where they both opened the same door on an entangled pair of boxes, they always get the same result. So far so good. But what happens when they look at the results as a whole? Well, Scully's theory was that these boxes are preprogrammed and the data we've collected falsifies this theory.
The only possible patterns, ignoring specific color and order, are ones where two windows reveal the same color and one window reveals another color (any ordering of GGR or RRG) or where all three windows open to the same color (GGG or RRR). In the latter case, their results will obviously match 100% of the time. In the former case, 2/3 of the time their results will match 2/3 of the time (for 4/9ths) and 1/3 of the time their results will match 1/3 of the time (for an additional 1/9th), adding up to 5/9ths.
So if Scully's theory is true, when opening doors at random, they should have recorded the same result at least 5/9ths of the time (more if some boxes are programmed with all windows revealing the same color).
Unfortunately for Scully, their records show that their results matched exactly 50% of the time. No matter how complicated your "programmed" hidden variable theory is (pseudorandom generators with the same seed, etc.), it is fundamentally disproven if the observed match rate is less than 5/9ths. The simplest explanation that fits this experimental result is that both boxes choose to display a color truly randomly when a given window is opened, but they both arrive at the same random color when the same window is opened!
Again, this statistical argument works against all hidden variable theories.
Re: NIST Physicists Show Ion Pairs Perform Enhanced 'Spooky Action'
#37Earlier quoted context omitted.
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…
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_m...
[...] 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.
Re: NIST Physicists Show Ion Pairs Perform Enhanced 'Spooky Action'
#38Earlier quoted context omitted.
I'm not sure your description of the difference between classical and quantum contradicts what I said. In fact I think they are compatible I didn't use any notion of "predetermination" when describing the quantum mechanical version. I said that "there could be several different degrees of freedom to measure on" I meant this to exactly correspond to "the exact outcome is only established when one looks in the first bo…
I was especially responding to this part. This (intuitively) makes more sense to me than saying "information traveled" and "action at a distance" You can not get away from non-locality in quantum mechanics. Because the outcome is only determined when a measurement is performed, this »information« has to travel to the entangled partner when the measurement is made. And this must happen instantaneously. In the classica…
I didn't/am not claiming that the effects are local.
> only determined at the time of the measurement... Before that measurement the electron had no definite spin along this axis.
That is what I'm saying as well. I didn't claim otherwise.