< Earlier Kibitzing · PAGE 27 OF 27 ·
|Nov-25-14|| ||Joshka: <sneaky> The pin wheel experiment didn't make sense to me, don't know how they can prove if the right wheel lands on black, the other one has to land on red. What really is astonishing about these matters is some physicists say nothing is real? we just imagine all the physical world, it's not really there????|
|Nov-25-14|| ||ernieb: We imagine how the universe looks to us, as individuals. There is no "real" universe to all, there is one determined by co-creation with some greater awareness and a basic universe, where particle matter is distributed over a field. The tiny amount of matter then gets pushed around and formed and perceived as each individual chooses, into a time/space framework. What "counts" is not then shared fact as absolute, as there is none, but the perception of creation in each viewpoint. Thus the Eastern model of "letting go" and seeing all things as one can solve the puzzle.|
|Nov-25-14|| ||Joshka: <ernieb> Then how would it look if no one was looking at it.......suppose a blind person (from birth) was the only person left on earth, and suddenly by a miracle his sight was restored, what would he observe?|
|Nov-26-14|| ||ernieb: If no one is looking at it, it is a black transparency with all matter at equivalent distance. However the instant it is perceived, this changes.|
|Nov-26-14|| ||al wazir: <Sneaky: This is often considered a big deal, and Einstein thought it represented "spooky action at a distance." I need somebody to walk me through exactly what is so mysterious.> Suppose the two labs are separated by a light year. The measurement at one lab determines the outcome of the measurement at the other *instantaneously*. It doesn't take a year. No speed-of-light lag.|
|Nov-26-14|| ||zanzibar: <sneaky> I watched more of the video from the start time you gave. |
It looks like Mermin has taken a more complicated example than he did back in 1985's <Physics Today Reference Frame> article <Is the Moon there when nobody looks?>.
I believe his new example is supposed to be more in line with the famous Aspect experiment, but I'm not entirely sure.
So, I'll have to watch the entire video and get back up to speed.
The conclusion is the same though, the individual particles are not independent - they form a quantum state, and so there are quantum correlations between measurements done on them. And these correlations cannot not be replicated with the hidden variables that a classical system must have.
|Nov-26-14|| ||zanzibar: <al wazir> < Suppose the two labs are separated by a light year. The measurement at one lab determines the outcome of the measurement at the other *instantaneously*. It doesn't take a year. No speed-of-light lag.>|
I don't like the phraseology used here.
<The measurement at one lab determines the outcome of the measurement at the other *instantaneously*.>
This statement implies a causal connection which is physically impossible.
The measurements are correlated, which is different from being causally connected.
|Nov-26-14|| ||zanzibar: Quantum Mechanics is full of paradoxes if you try to put it into a classical box.|
Consider a couple of quick examples:
1) You can rotate a physical system by 360 degrees and it is not identical to the system before rotating (e.g. a spin 1/2 electron).
2) You can shoot an electron through a double slit and obtain an interference pattern on a screen behind it (so that the electron interferes with itself).
Now, place a very thin solenoid between the two slits (B field parallel to wall with slits). The solenoid completely contains the magnetic field, but is so small and close to the wall that you are guaranteed that the electrons never pass through it.
The interference pattern on the screen will shift, according to how strong the field is inside the solenoid, despite the fact that the electrons never pass through any space with a non-zero magnetic field.
3) You can trap an alpha particle inside a potential well in a nucleus of an atom. The potential is so high that the alpha particle will never have sufficient energy to cross over.
Yet the alpha particle can quantum mechanically tunnel out, and the nucleus decay. (Note that energy is conserved, provided you only observe the alpha particle inside or outside the potential well).
Any one of these items are complete paradoxes, unexplainable by classical physics.
The EPR paradox (or quantum entanglement) is just another example.
|Nov-26-14|| ||zanzibar: Mermin's homepage:
has notes to his <Spooky Action at a Distance> talk:
|Nov-26-14|| ||al wazir: <zanzibar: This statement implies a causal connection which is physically impossible.> It's been verified experimentally. Sorry about that.|
I think you're being misled by your envelope analogy. Even if you don't know what's in the envelope, whatever is there doesn't change. It is what it is. Not so with electrons or photons. Each electron is in a *superposition* of two states, spin up and spin down. It is *not* definitely one or the other.
Imagine that in two labs a coin is tossed. Suppose that the coins are correlated in the same fashion as electrons. Each coin can land heads or tails with equal probability; but whichever way it falls, *the coin in the other lab has to fall the other way* -- even if the labs are a light year apart. Why do they do that? Because (by my assumption) they obey the laws of quantum mechanics.
|Nov-26-14|| ||zanzibar: <al wazir> OK, but the state isn't|
|1>|2> implying two independent particles (somehow correlated).
The state is |1,2>.
The mystery is quantum measurement, having two particles (even if separated by a space-like interval) isn't different from having one particle.
You make a measure and have determined the state. Be it one particle or two.
What's the difference?
|Nov-26-14|| ||Shams: <al wazir> Weren't you the one who said, a year or so ago, that quantum entanglement only seems to imply action at a distance but doesn't really?|
|Nov-26-14|| ||al wazir: <Shams: Weren't you the one who said, a year or so ago, that quantum entanglement only seems to imply action at a distance but doesn't really?> Probably. (I could answer with some flip line about how I'm in a superposition of two states, "yes" and "no," but I won't.)|
Correct me if I'm wrong: I haven't used the expression "action at a distance." <Zanzibar> did.
|Nov-26-14|| ||nok: <quantum entanglement only seems to imply action at a distance but doesn't really?> Indeed. When one party updates its information, it doesn't mean the description of the other party is wrong.|
|Nov-26-14|| ||Shams: <al wazir> No I think you're right. I'm just trying to follow along, please ignore me.|
|Nov-26-14|| ||chancho: Albert Einstein, a real Player:
|Nov-26-14|| ||WannaBe: Chicks dig the long (differential) equations.
(Apologies to the MLB ad)
|Nov-26-14|| ||zanzibar: <al> but you did the word instantaneous(ly), which amounts to the same thing. |
And the statement <It's been verified experimentally.> also needs care.
<QM> has been verified experimentally - not the instantaneous transmission of information which I think you're suggesting.
The current standard model of physics has nothing going faster than the speed of light.
(The advanced Green's functions get throw out by hand)
* * * * *
OK, I admit the envelop analogy is flawed, since it suggests hidden variables.
I go back to the teeter-totter analogy.
If you have conversation of angular momentum and a spin-zero decay of positronium, you will always find one end down when the other is up. (|1R,2L> or |1L,2R>).
Again, suppose I have a single particle system with L,S degrees of freedom. Suppose L can be a or b, while S can also be a or b.
Start with a QM superposition:
1/sqrt(2)( |L(a),S(a)> + |L(b),S(b)> )
Now if I make a measure on L and get |L(a)> I know I get |S(a)> too. Even if I wait to measure S. That's because it's a quantum state, but it's not so mysterious.
What's the difference of a one-particle, two degrees of freedom quantum state and a two-particle, one degree of freedom quantum state.
You make a measurement, you find the state, and you know something about the part of the state you didn't measure.
Because the correlation is built into the state.
QM states are mysterious, not the two particles flying off to infinity.
|Nov-26-14|| ||zanzibar: Sorry, but to be explicit:
<<al> but you did the word instantaneous(ly), which amounts to the same thing.>
The <same thing> being action-at-a-distance (whether it's force or information transfer).
|Nov-26-14|| ||al wazir: <zanzibar: And the statement <It's been verified experimentally.> also needs care. <QM> has been verified experimentally - not the instantaneous transmission of information which I think you're suggesting.> No, *information* is not transmitted instantaneously. |
Here, from the wiki article on"quantum entanglement," is a summary of the current state of affairs: <Schrödinger was dissatisfied with the concept of entanglement, because it seemed to violate the speed limit on the transmission of information implicit in the theory of relativity. Einstein later famously derided entanglement as "spukhafte Fernwirkung" or "spooky action at a distance." The EPR paper generated significant interest among physicists and inspired much discussion about the foundations of quantum mechanics (perhaps most famously Bohm's interpretation of quantum mechanics), but produced relatively little other published work. So, despite the interest, the flaw in EPR's argument was not discovered until 1964, when John Stewart Bell proved that one of their key assumptions, the principle of locality, was not consistent with the hidden variables interpretation of quantum theory that EPR purported to establish. Specifically, he demonstrated an upper limit, seen in Bell's inequality, regarding the strength of correlations that can be produced in any theory obeying local realism, and he showed that quantum theory predicts violations of this limit for certain entangled systems. His inequality is experimentally testable, and there have been numerous relevant experiments, starting with the pioneering work of Freedman and Clauser in 1972 and Aspect's experiments in 1982. They have all shown agreement with quantum mechanics rather than the principle of local realism. However, the issue is not finally settled, as each of these experimental tests has left open at least one loophole by which it is possible to question the validity of the results.> http://en.wikipedia.org/wiki/Quantu...
Here's the experimental test (cited above) that confirmed "spookiness": http://journals.aps.org/prl/abstrac...
|Nov-26-14|| ||al wazir: From the same article (I should have copied this instead of what I just posted): <Experiments have been performed involving measuring the polarization or spin of entangled particles in different directions, which—by producing violations of Bell's inequality—demonstrate statistically that the local realist view cannot be correct. This has been shown to occur even when the measurements are performed more quickly than light could travel between the sites of measurement: there is no lightspeed or slower influence that can pass between the entangled particles. Recent experiments have measured entangled particles within less than one part in 10,000 of the light travel time between them. According to the formalism of quantum theory, the effect of measurement happens instantly. It is not possible, however, to use this effect to transmit classical information at faster-than-light speeds (see Faster-than-light → Quantum mechanics).>|
|Nov-26-14|| ||zanzibar: <al wazir> ok then, the paper you cite is the Aspect paper.|
The wiki use of <local realism> is what I would call <hidden variables> I think.
Mermin's work from 1985 was basically inspired by the recent Aspect et al experiment:
<Experimental Realization of Einstein-Podolsky-Rosen-Bohm Gedankenexperiment: A New Violation of Bell's Inequalities
Phys. Rev. Lett. 49, 91 – Published 12 July 1982>
It is expected to violate Bell's Inequalities if <QM> is correct.
I believe there are other even larger measured violations subsequent to the 1982 result. I have to look it up...
According to this 2013 book:
<The Quantum Divide (2013)>
The largest observed violation (at 1200 std) is from a 2005 expt by Altepeter, Jeffery, Kwiat at U. Illinois.
The abstract is here:
<Here we present experimental realizations of two new entanglement detection methods: a three-measurement Bell inequality inequivalent to the Clauser-Horne-Shimony-Holt inequality and a nonlinear Bell-type inequality based on the negativity measure. In addition, we provide an experimental and theoretical comparison between these new methods and several techniques already in use: the traditional Clauser-Horne-Shimony-Holt inequality, the entanglement witness, and complete state tomography.>
The three measurement idea probably inspired Mermin's more involved gerdankin used in his Berkeley talk.
|Nov-26-14|| ||zanzibar: <al> I assume <According to the formalism of quantum theory, the effect of measurement happens instantly.> was copied from a wiki article and not a PRL or other physics paper?|
|Nov-27-14|| ||al wazir: <zanzibar: I assume <According to the formalism of quantum theory, the effect of measurement happens instantly.> was copied from a wiki article and not a PRL or other physics paper?> Yes. I apologize for leaving that ambiguous.|
|Nov-27-14|| ||Joshka: <ernieb> That's absurd. We observe what is there cause we CAN SEE IT!! To nail your statement in a very clear example: You are saying the moon is only there cause we can observe?? It's not really there??LOL|
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