What's all this about, then ??

[CraigS]

Ok … so we've got a couple of good ol' down-to-earth astronomy & discovery of new life threads running … so here's another one (with no deliberate intentions of offending the practical types out there, either).

If you thought Black Hole collisions and Holographic Universes was estoteric, avoid this one at all costs !!

So here goes … how else could anyone explain this and maintain credibility, without using the principles and mathematics behind quantum mechanics ? (Not that I understand what they are in the first place !! )

Physicists close two loopholes while violating local realism

The latest test in quantum mechanics provides even stronger support than before for the view that nature violates local realism and is thus in contradiction with a classical worldview.
…
local realism consists of both realism – the view that reality exists with definite properties even when not being observed and;
locality – the view that an object can only be influenced by its immediate surroundings. If a Bell test shows that a measurement of one object can influence the state of a second, distant object, then local realism has been violated.

They go on to say that they've conducted an experiment splitting entangled photons then sending them over two physically different paths - one 144kms and the other, 6 kms, measured one of the received ones, and it still effects the other one. Only this time, they've ruled out 2 of the 3 known areas of doubt which could've influenced the measurement.

This stuff has been going on for years now, but its starting to look like everyone is running out of ideas to disprove the observation of entanglement !!

Nature is just bizarre …. !!

Cheers

[Robh (Rob)]

Craig,

Interesting that you mentioned the Holographic Universe here.
I believe you can cut a hologram in half and each half will still display the same image ...
http://science.howstuffworks.com/hologram.htm
In other words, the parts of the hologram have the same information as the whole.

Well, apparently in a holographic universe, each part of the universe contains information about the entire universe. This information is "encoded" at its boundary in the cosmic event horizon. The projection from this 2 dimensional boundary creates the "reality" (or illusion) of 3 dimensional space and its matter. From what I've read, Bell's Theory and quantum entanglement would fit quite happily into the Holographic Universe.

Regards, Rob

[CraigS]

Hmmm .. thanks for that, Rob.

Very interesting. I never knew that about holograms.

I'm still trying to digest Bell's experiment/theory so I'm not really able to comment, just yet.

My mind just keeps coming back to: "Where is the connection to make this entanglement thing work ? What is it ?"

I think you're suggesting information encoded at the cosmic horizon (?)

What ever it is, it seems pretty clear that there's something very fundamental, which we just can't figure out yet, which makes all this happen.

The holographic principle and quantum mechanics are related through string theory, but all of this is created by human ingenuity. Somehow, the relationship between spins on separated, entangled photons would seem to me, to be caused by something other than human ingenuity.

But then again, until they close that final loophole, perhaps that IS the missing link !!??

Incredible stuff !!

(Lots more reading to do on this ….. not Mathis or Gaede, though )

Cheers

[sjastro]

I'm still trying to digest Bell's experiment/theory so I'm not really able to comment, just yet.

Bell's inequality is based on a wonderful piece of logic in the macro world.
The violation of Bell's inequality in photon polarization tests was a blow to Einstein's (and others) local hidden variable theory and supported the idea for quantum entanglement.

Regards

Steven

[CraigS]

Originally Posted by sjastro

Bell's inequality is based on a wonderful piece of logic in the macro world.
The violation of Bell's inequality in photon polarization tests was a blow to Einstein's (and others) local hidden variable theory and supported the idea for quantum entanglement.

Regards

Steven

So, I'm having a lot of difficulty in translating all this into plain English.

Is it reasonable to say that Bell's theorem is saying that faster than light changes can happen, and can be reproduced as per quantum mechanical predictions, whereas Special Relativity says this cannot happen ?

I'm mystified as to whether any of these concepts are implying anything about the causes of entanglement.

It seems to be more about predictions of correlated events (??)

Cheers

[sjastro]

Originally Posted by CraigS

So, I'm having a lot of difficulty in translating all this into plain English.

Is it reasonable to say that Bell's theorem is saying that faster than light changes can happen, and can be reproduced as per quantum mechanical predictions, whereas Special Relativity says this cannot happen ?

I'm mystified as to whether any of these concepts are implying anything about the causes of entanglement.

It seems to be more about predictions of correlated events (??)

Cheers

Craig,

Here is simple example of the significance of Bell's Inequality for an experiment.

Suppose you performed a machine washability test on gloves at different temperatures. The gloves are dyed in different colours but are made of the same material. Let's assume that the dye is stable at all temperatures and doesn't wash off. Hence each glove is expected to react in the same way when tested. By testing large numbers of gloves you can calculate the probabilities of whether or not the gloves survive a test at a given temperature.
The probabilities are the same if you are testing left hand gloves or right hand gloves.
If you pair off the gloves according to their colours, the probabilities are still the same. This is because the result on a left hand glove doesn't effect the result on a right hand glove and vice versa for any given test.

For this test Bell's inequality isn't violated as the left hand and right hand gloves have separate realities. Each glove has a local reality.

Local hidden variable theories which maintain that local reality exists, run into trouble when for example the test on a right hand (or left hand) glove does effect the other glove. Since the gloves have a separate reality and exist at different points in space-time there must be an instantaneous transfer of information which of course would exceed the speed of light.

When Bell's inequality is violated this means there cannot be separate realities. In the case of a pair of photons, the photons exist in a delocalized or entangled state.
The photons are in "contact" prior to a measurement being made in an experiment.

Regards

Steven

[CraigS]

Thanks Steven;

Hmmm … so, the photons, (in "contact") initially, exist at a specific, unique point in spacetime. Somehow, the properties of one of the photons, gets changed by a later measurement, which then appears to cause a change in the other, no matter how much separation between, or how much later, the measurements are made (??)

If I have this right, then there are no statements in the above made about the cause of the entanglement (or initial "contact"). The thing about this entanglement thing is that the measurement of one effects the other's state after they becomes physically and temporally separated (?)

So, it seems that they are still trying to eliminate the possibility that the local environmental test conditions at the 'primary test site doesn't somehow, interact to influence the outcome at the secondary test site (?).

Once they've pinned this down, the conclusion would be as you have said .. the entanglement is established by something going on initially, rather than later (?)

But what keeps the two photons in contact ? I guess this is the BIG question, huh ?

(Gaede says 'a twisted, invisible rope' !! … he's a legend, y'know !! )

Cheers
PS: I'm not asserting anything here .. I'm just trying to 'align' myself with the concepts. (Except the Gaede comment )

[sjastro]

Originally Posted by CraigS

Thanks Steven;

Hmmm … so, the photons, (in "contact") initially, exist at a specific, unique point in spacetime. Somehow, the properties of one of the photons, gets changed by a later measurement, which then appears to cause a change in the other, no matter how much separation between, or how much later, the measurements are made (??)

If I have this right, then there are no statements in the above made about the cause of the entanglement (or initial "contact"). The thing about this entanglement thing is that the measurement of one effects the other's state after they becomes physically and temporally separated (?)

So, it seems that they are still trying to eliminate the possibility that the local environmental test conditions at the 'primary test site doesn't somehow, interact to influence the outcome at the secondary test site (?).

Once they've pinned this down, the conclusion would be as you have said .. the entanglement is established by something going on initially, rather than later (?)

But what keeps the two photons in contact ? I guess this is the BIG question, huh ?

(Gaede says 'a twisted, invisible rope' !! … he's a legend, y'know !! )

Cheers
PS: I'm not asserting anything here .. I'm just trying to 'align' myself with the concepts. (Except the Gaede comment )

Perhaps I shouldn't have used the term "contact" (even if it was in inverted commas) because it does convey the wrong impression.

In QM there is a role played by the experiment, the observer and in this case, the pair of photons. An experiment can produce a number of outcomes, each outcome has a particular probabilty of occurring. The role of the observer in QM is to make a measurement. When the measurement is made the outcome is determined.
Before a measurement is made the photons exist in a superimposed state of all the possible outcomes. In the case of a pair of photons in a polarization test, the photons cannot be distinguished in the superimposed state. This defines entanglement.

Entanglement doesn't mean physical contact, rather a mixing of all the possible outcomes of the experiment for each photon.

Regards

Steven

[Robh (Rob)]

Bell's Theorem is a consequence of the violation of Bell's Inequality.
Loosely stated the theorem says ... "No physical theory of local hidden variables can ever reproduce all of the predictions of quantum mechanics." (from wikipedia).

"According to the quantum entanglement theory of quantum mechanics, on the other hand, distant events may under some circumstances have instantaneous correlations with local ones." (from wikipedia).

This is a fairly readable account of Bell's Theorem.
Even so, it takes some time and effort to wade through.
http://www.upscale.utoronto.ca/PVB/H...lsTheorem.html

"Believe me when I tell you that I'm not that honest" (see document text for relevance).

Regards, Rob

[CraigS]

Hmm .. thanks Rob and Steven;

It seems one needs to be careful about what one reads on this subject.

Wiki's opening paragraph on entanglement is kind of where I was coming from in my last post to Steven, (although, I have read this interpretation elsewhere):

Quantum entanglement, also called the quantum non-local connection, is a property of certain states of a quantum system containing two or more distinct objects, in which the information describing the objects is inextricably linked such that performing a measurement on one immediately alters properties of the other, even when separated at arbitrary distances.

However, further down it says:

When each of the particles in the entangled pair is measured in the same way, the results of their spin measurement will be correlated. Measuring one member of the pair tells you what the spin of the other member is without actually measuring its spin.

There's a big difference between saying one's spin is correlated with the other, and saying that the measurement itself alters the other's spin.

So which one should I believe ?

Cheers

[sjastro]

Originally Posted by CraigS

Hmm .. thanks Rob and Steven;

It seems one needs to be careful about what one reads on this subject.

Wiki's opening paragraph on entanglement is kind of where I was coming from in my last post to Steven, (although, I have read this interpretation elsewhere):

However, further down it says:

There's a big difference between saying one's spin is correlated with the other, and saying that the measurement itself alters the other's spin.

So which one should I believe ?

Cheers

Craig,

I think the first quote is a bit vague and the term properties is perhaps not the best description.

The first quote is similiar to my previous post. Before a measurement is made the entangled state is a superimposed state of various possible outcomes. Measuring a state of a particle, also changes the state of the unmeasured partcle. You can't have the measured particle in a particular state and the unmeasured particle still in a superimposed state. Both particles are either in a particular state or both are in a superimposed (unmeasured state). The measurement doesn't have to be spin. It could be for example energy or angular momentum.

The second quote refers to a particular property of spin. For fermions the state is either spin up or spin down. In the entangled state the fermion pair have opposing spins. This is due to the Pauli exclusion principle.

When a measurement is made, if the measured particle is spin up the other particle must be spin down (or vice versa). No measurement of the spin state of the second particle is required if the spin state of the measured particle is known. The spin state of each particle will always be opposite.

Hope this clarifies things.

Steven

[CraigS]

Thanks Steven;
I understand your explanation.
I think I'll go into doing some more reading before I go any further on this.

There's something bugging me about it all (it has since I first encountered it, and it hasn't changed. I can't remember exactly what it is, so I'll have to do a refresh).

Cheers

[Robh (Rob)]

I like some of these experiments of spooky behaviour ...
http://www.davidjarvis.ca/entanglement/spookiness.shtml

Nice illustrations of quantum entanglement.

Regards, Rob

[CraigS]

Hey Rob;

Thanks for that .. a cool summary of some of the experiments!

It co-incides with what I was reading up, on last night.

The last experiment in your link, is the one which characterises the problem, for me.

I was also reading about quantum probability waves, (which seem to be the quantum explanation for all this):

according to quantum mechanics, every probability wave extends throughout all of space, throughout the entire universe …
...
so long as the probability wave somewhere in the Andromeda galaxy has a nonzero value, no matter how small, there is a tiny but genuine non-zero chance, that say, a partner entangled electron, could be found there.

So in the last experiment from your link, perhaps the probability wave, (between the entangled photons), also extends to the location of Detector A, thus the relationship, (or connection), IS the probability wave of the photon partner at Detector B.

Pretty tricky explanation, though. It seems both photons are undergoing 'detection' so this influences the outcomes at both location as well. (??)

Cheers

[avandonk]

I personally think that quantum entanglement is telling us something very deep about reality.

When fluorinated bucky balls 'interfere' with themselves when there is only one particle in the diffraction experiment to produce a diffraction pattern you have to say this is totally absurd!

The concept basically that all wave functions follow all possible paths and it is only when the wave functions collapse that we get 'reality'.

This basically is saying that all matter is linked by an intrinsic infinite wave function associated with each particle that is everywhere non zero.

It further seems to act instantly so being faster than light. It must be other dimensional to do this.

Bert

[CraigS]

I didn't know that about bucky-balls ! Fascinating !
(Could you 'slip us a link' on that one, Bert ?)

About probability wave functions:
It really is amazing isn't it ?
There's something about the observer becoming a player in the outcome which tells us something, also. That we could influence a particle elsewhere in the galaxy, simply by measuring its partner's properties here, suggests something about bridging vast distances, in faster-than-light speeds, also.

Its almost teleportation, of sorts !

Cheers

[joe_smith]

This is a fairly readable account of Bell's Theorem.
Even so, it takes some time and effort to wade through.
http://www.upscale.utoronto.ca/PVB/H...lsTheorem.html

I have been reading this and found this part intriguing

In one analogy he imagined a large cylindrical glass container of glycerine mounted on a turntable. We place a spot of black ink in the glycerine. We slowly rotate the container, and the ink gradually disperses throughout the glycerine. If we slowly rotate the cylinder in the opposite direction the spot of ink gradually re-forms

I thought this was just an "analogy" but while looking into it more I found a video and I would never of believed that it is possible, you actually can do this

[CraigS]

Originally Posted by joe_smith

I have been reading this and found this part intriguing
...
I thought this was just an "analogy" but while looking into it more I found a video and I would never of believed that it is possible, you actually can do this

Hi Joe_Smith;

Fascinating !! .. I never knew this ! (I reckon their price of $US450 for the Couette Cell, and $US50 for the plans is a bit steep, though !)

I guess, in spite of its everyday occurrence around us, we probably never stop to contemplate the concepts behind pure laminar flows.

When I looked at the video, I was amazed. I was also reminded of that giant hexagonal feature on the north pole of Saturn. One hypothesis proposed is that this feature may be due to laminar flows of the winds in that region .. and was demonstrated by the same notorious, perspex spinning bucket !!

Also makes one wonder whether the Great Red Spot of Jupiter, (etc) is held together by the same physics (ie: likely).

Thanks for your input. It really is a fascinating topic.

Cheers

[CraigS]

Here's more mystical 'evidence' …

Quantum theory survives latest challenge

Four years later, physicists in Austria, Switzerland and Singapore answered with data. Instead of measuring the linear polarization states used to violate Bell’s inequality they looked for correlations between elliptical polarizations – combinations of linear and circular states. Even assuming that entangled photons could respond to one another instantly, the correlations between polarization states still violated Leggett’s inequality. The conclusion being that instantaneous communication is not enough to explain entanglement and realism must also be abandoned.

This conclusion is now backed up by Sonja Franke-Arnold and collegues at the University of Glasgow and University of Strathclyde who have performed another experiment showing that entangled photons show stronger correlations than allowed for {in} particles with individually defined properties – even if they would be allowed to communicate constantly. But rather than polarization, they studied the properties of each photon’s orbital angular momentum.

This whole thing is starting to look just as Bert mentioned.

Ie: each particle should be viewed as the one particle appearing in both places at the same time and the 'connection' between them is beginning to look 'extra-dimensional'.

Cheers