Demystifying Quantum Physics

[zaybu]

In QM, nonlocality can occur in certain experimentally-constructed situations which are not necessarily typical in Nature. An entangled pair of particles may be separated by a great distance, while being careful not to let them interact too much with the environment, and then the particles may be measured simultaneously by distant observers. After the experiment, when the observers get together and compare their data, they will notice certain statistical correlations. It has been shown, theoretically and experimentally, that these correlations must have occurred due to an instantaneous influence of one entangled particle on its distant partner.

Sorry but that is totally wrong. There is no spooky action at a distance. There is no need of hidden parameters. And no signal was sent faster than the speed of light. It simply means that if two particles are "entangled", it means that they were prepared in a given quantum state, and unless there is an interaction, they will continue to stay in that quantum state.

 

[idav]

Sorry but that is totally wrong. There is no spooky action at a distance. There is no need of hidden parameters. And no signal was sent faster than the speed of light. It simply means that if two particles are "entangled", it means that they were prepared in a given quantum state, and unless there is an interaction, they will continue to stay in that quantum state.

I don't think that locality is being violated with entanglement since the particles had to have interacted with something at some point to give it a particular quantum state. And right, nothing goes faster than the speed of light, relativity is still true far as I know.

 

[zaybu]

I don't think that locality is being violated with entanglement since the particles had to have interacted with something at some point to give it a particular quantum state. And right, nothing goes faster than the speed of light, relativity is still true far as I know.

Of course, to have a pair of entangled particles, they had to be put in that state in the initial stage, which mean there was interaction prior to make them entangled. They don't become entangled on their own. It's understood the system has to be prepared in a particular way. But the spookiness that is often referred to is what happens after the entanglement was done, and, contrary to what was said in this thread by some, there's no spookiness.

 

[Mr Spinkles]

You can make even quantum nonlocality go away by keeping careful track of what you're doing and which way wavefunctions are propagating.

Sorry but that is totally wrong. There is no spooky action at a distance. There is no need of hidden parameters. And no signal was sent faster than the speed of light. It simply means that if two particles are "entangled", it means that they were prepared in a given quantum state, and unless there is an interaction, they will continue to stay in that quantum state.

I don't think that locality is being violated with entanglement since the particles had to have interacted with something at some point to give it a particular quantum state. And right, nothing goes faster than the speed of light, relativity is still true far as I know.

Gentlemen: what I described is quantum nonlocality as it is understood by most of the physics community and described in standard elementary quantum mechanics textbooks (such as Griffiths). Differences of taste in interpretation notwithstanding, what I said was not "wrong". For your reference, see the following articles in the journal Nature:

That nature is non-local, in the sense of so-called Bell-inequality violations, is by now well known. That is, quantum physics allows correlations between distant particles that are stronger than allowed classically: for classical systems to show such correlations they would need to communicate faster than light. Understanding this kind of non-locality and using it is one of the greatest achievements of quantum information science.

http://www.nature.com/nphys/journal/v6/n3/full/nphys1619.html
http://www.nature.com/ncomms/journal/v2/n2/full/ncomms1193.html
http://www.nature.com/nature/journal/v403/n6769/full/403515a0.html

Bell's theorem1 states that certain statistical correlations predicted by quantum physics for measurements on two-particle systems cannot be understood within a realistic picture based on local properties of each individual particle—even if the two particles are separated by large distances.
...
We find the results of the fourth experiment to be in agreement with the quantum prediction and in striking conflict with local realism.

There is certainly limited room for alternative interpretations of quantum mechanics, although the remaining comfortable room available to a "local" interpretation has been running out. I chose to only discuss the mainstream interpretation because (1) it is the most generous interpretation with respect to my opponents, Deepak Chopra and those who follow his brand of quantum-mysticism, and (2) it simplifies the discussion. I hardly think it could be productive to try to enter into a debate with the world's leading physicists on the finer philosophical points of alternative interpretations of QM, when the basic science is already too much for Chopra et al. to get straight.

 

[Mr Spinkles]

As it turns out, if you use the Heisenberg uncertainty principle to calculate the uncertainty in the position of a typical baseball, the answer is ~10^-8 mm, or 0.00000001 mm. That's about 1/10th the width of a single atom! In other words, ordinary objects like baseballs have an extremely well-defined position.

Correction: the answer is closer to 10^-30 mm, or 0.000000000000000000000000000001 mm, which is around one billion billion millionth the size of an atom. (I knew that other number couldn't be right, how embarrassing! ) Anyway, hopefully you get the idea: the number is incredibly small.

Can any Mods edit my OP appropriately? Thanks.

 

[godnotgod]

Your referencing the author to back up your ideas, are you not. You agree with the authors paraphrasing?

Yes, and the text you highlighted is not making intuition 'more than it is', as you claim. What 'more than it is' do you see?

 

[Penumbra]

Can any Mods edit my OP appropriately? Thanks.

I put your new number into the OP, so it should be good now.

 

[Penumbra]

[youtube]wcXSpXyZVuY[/youtube]
Seth Lloyd on Quantum Life - YouTube

I watched this the other day where this fellow from MIT said that, in some limited instances that are known so far, biology makes use of some quantum effects. The most well-evidenced example he gives is for absorption of solar energy by single-celled organisms. Another one is where noses, including the human nose, indirectly makes use of quantum mechanics. The most speculative example had to do with bird navigation.

 

[LegionOnomaMoi]

(2) it simplifies the discussion.

But you missed the most important stuff, like how the world is a hologram (holographic, of course, means absolutely the same thing whether one is talking about techincal literature in cosmology or watching Star Wars).

 

[Mr Spinkles]

I watched this the other day where this fellow from MIT said that, in some limited instances that are known so far, biology makes use of some quantum effects. The most well-evidenced example he gives is for absorption of solar energy by single-celled organisms. Another one is where noses, including the human nose, indirectly makes use of quantum mechanics. The most speculative example had to do with bird navigation.

Don't get me wrong, that sort of research is very cool. Scientists are very interested. However, the layperson and the philosopher may need a bit of context here: chemistry is a quantum effect. The real nitty-gritty details of how a protein catalyzes a reaction, or fluoresces in response to light, or how the atoms in DNA can be linked by covalent bonds of "shared" electrons---these are all quantum effects. In a sense, therefore, the new "quantum biology" stuff is just an additional cool, unexpected way that life takes advantage of, and generates new kinds of, chemistry (or photochemistry). In that sense, I don't think it is groundbreaking from a philosophical perspective. From a scientific perspective, however, it is very cool and interesting because we didn't expect biochemistry could take advantage of these particular quantum effects, which feel a bit "more quantum" than traditional chemistry (but perhaps that's just because we take it for granted in chemistry). That's just my opinion, anyway, FWIW.

 

[zaybu]

There is certainly limited room for alternative interpretations of quantum mechanics, although the remaining comfortable room available to a "local" interpretation has been running out. I chose to only discuss the mainstream interpretation because (1) it is the most generous interpretation with respect to my opponents, Deepak Chopra and those who follow his brand of quantum-mysticism, and (2) it simplifies the discussion. I hardly think it could be productive to try to enter into a debate with the world's leading physicists on the finer philosophical points of alternative interpretations of QM, when the basic science is already too much for Chopra et al. to get straight.

As long as you understand that "non-locality" means there are no hidden local parameters. My initial objection was to the statement: "that these correlations must have occurred due to an instantaneous influence of one entangled particle on its distant partner." That is wrong.

 

[LegionOnomaMoi]

Sorry but that is totally wrong. There is no spooky action at a distance. There is no need of hidden parameters. And no signal was sent faster than the speed of light. It simply means that if two particles are "entangled", it means that they were prepared in a given quantum state, and unless there is an interaction, they will continue to stay in that quantum state.

As long as you understand that "non-locality" means there are no hidden local parameters. My initial objection was to the statement: "that these correlations must have occurred due to an instantaneous influence of one entangled particle on its distant partner." That is wrong.

Mr. Sprinkles isn't very familiar with things like quantum mechanics, particles, etc. It's waayyyy outside his field. He's a physicist, not a....oh, wait. Those are the people that actually study these things.

Also, FYI, "spooky action at a distance" is accepted by virtually everybody in the physics community.
Experimental demonstration of quantum correlations over more than 10 km.

Quantum Nonlocality without Entanglement

Quantum non-locality in two three-level systms

Experimental quantum teleportation

However, I have no doubt that your work with Bell's inequalities has demonstrated alternative explanations for correlations between space-like seperated photon pairs at distinces of 10+ kilometers.

 

[zaybu]

Also, FYI, "spooky action at a distance" is accepted by virtually everybody in the physics community.

Experimental demonstration of quantum correlations over more than 10 km.

If you read this article properly, you won't find any "spooky action at a distance." Their conclusion is:
1. These strong nonlocal correlations support the nonlocal predictions of quantum mechanics.

2. and provide evidence that entanglement between photons can be maintained over long distances.

Quantum Nonlocality without Entanglement
None here


Quantum non-locality in two three-level systms

None here

Experimental quantum teleportation

None here.

Do you read your links, or you just throw them to intimidate people?

However, I have no doubt that your work with Bell's inequalities has demonstrated alternative explanations for correlations between space-like seperated photon pairs at distinces of 10+ kilometers.

I doubt very much you understand Bell's theorem. And it certainly is not about spooky action at a distance.

 

[LegionOnomaMoi]

If you read this article properly, you won't find any "spooky action at a distance."
Their conclusion is:
1. These strong nonlocal correlations support the nonlocal predictions of quantum mechanics.
2. and provide evidence that entanglement between photons can be maintained over long distances.

What exactly do you think Einstein meant by spukhafte Fernwirkung?

It doesn't matter. Here:
"Einstein called the instantaneous interaction of the spatially separated spins “spukhafte Fernwirkungen” (spooky action at a distance). He did not accept the possibility of such spooky action and, because quantum mechanics appeared to demand it, it had to be at least incomplete. The Bell theorem and its standard interpretation have turned the logic around. Its supporters now claim that local hidden parameters do not exist and cannot explain the EPR experiments. Quantum mechanics does agree with these experiments, and spooky action at a distance must be accepted as a fact of nature." (link to this PNAS study)

Do you read your links, or you just throw them to intimidate people?

Yes. I have no idea what I'm talking about or what Einstein meant or anything whatsoever about quantum mechanics.

I doubt very much you understand Bell's theorem. And it certainly is not about spooky action at a distance.

And neither is EPR. Because spooky action at a distance clearly refers to...?

 

[zaybu]

What exactly do you think Einstein meant by spukhafte Fernwirkung?

It doesn't matter. Here:
"Einstein called the instantaneous interaction of the spatially separated spins “spukhafte Fernwirkungen” (spooky action at a distance). He did not accept the possibility of such spooky action and, because quantum mechanics appeared to demand it, it had to be at least incomplete. The Bell theorem and its standard interpretation have turned the logic around. Its supporters now claim that local hidden parameters do not exist and cannot explain the EPR experiments. Quantum mechanics does agree with these experiments, and spooky action at a distance must be accepted as a fact of nature." (link to this PNAS study)

Again you provide a link that doesn't support your claim. Here the author is looking at the possibility of finding loophole into Bell's theorem. In what way does that support your claim of spooky action at a distance? None whatsoever.

Secondly, do you know that Einstein was wrong about spooky action at a distance, and none of those people who have carried his torch were not able to prove it?

Yes. I have no idea what I'm talking about or what Einstein meant or anything whatsoever about quantum mechanics.

For once I will agree.

 

[LegionOnomaMoi]

"A good way of thinking about such apparent instantaneous “spooky action at a distance” (as Einstein put it) is to realize that the entangled state must have been prepared locally by having let the two subsystems interact at some point in the past. When these two subsystems are then separated from each other, the quantum state is simply “spread out” (i.e., delocalized) over a larger spatial region." p. 31

Schlosshauer, M. A. (2007). Decoherence: and the quantum-to-classical transition. Springer Verlag.

"John Stewart Bell further drew out the counter-intuitive implications of the presence of entangled states in quantum theory by delimiting the border between local classically explicable behavior and behavior that is not locally causal, with a theorem involving an inequality. This inequality must be obeyed by local (hidden-variables) theories that might be introduced in order to explain all correlations between two distant subsystems forming a compound system, such as one described by the above state when the particles are well separated. Schrödinger believed that such states of widely separated subsystems could not be realizable in practice. However, it was subsequently found to be violated in essence by a broad range of quantum-mechanical systems, such as a pair of photons in the singlet state of Equation 1.21. Bell-type theorems are discussed further in Section 1.8, below. When asked to describe his theorem in “plain English,” Bell said that
'It comes from an analysis of the consequences of the idea that there should be no action at a distance, under certain conditions that Einstein, Podolsky, and Rosen focussed attention on in 1935—conditions which lead to some very strange correlations as predicted by quantum mechanics.'" p. 20
Jaeger, G. (2009). Entanglement, information, and the interpretation of quantum mechanics. Springer.

"The constructive answers to all these questions are prepared by providing detailed background information and the important answer to one of these fundamental questions is that experiments confirm that “spooky action at a distance” takes place in the K-meson system"
Brning, E., & Petruccione, F. (2009). Theoretical Foundations of Quantum Information Processing and Communication: Selected Topics. Springer

Do you require more citations/references?

 

[idav]

What exactly do you think Einstein meant by spukhafte Fernwirkung?

It doesn't matter. Here:
"Einstein called the instantaneous interaction of the spatially separated spins “spukhafte Fernwirkungen” (spooky action at a distance). He did not accept the possibility of such spooky action and, because quantum mechanics appeared to demand it, it had to be at least incomplete. The Bell theorem and its standard interpretation have turned the logic around. Its supporters now claim that local hidden parameters do not exist and cannot explain the EPR experiments. Quantum mechanics does agree with these experiments, and spooky action at a distance must be accepted as a fact of nature." (link to this PNAS study)

How is it that that there are no hidden variables when nobody really knows how QM does this "spooky" action? Everything in this universe has to deal with locality and cause and effect even in the QM world. This is why we have people like Chopra end up chalking it all up to reality being a dream and other hocus pocus type solutions.

 

[LegionOnomaMoi]

Again you provide a link that doesn't support your claim.

Because I didn't care what the paper was supposed to show. I chose it because
1) Most people would agree that PNAS is a fairly reputable journal, and while not as technical and carefully reviewed as Scientific American or The Wall Street Journal, it does have a reputation like other minor journals such as Science, Nature, Physical Review Letters, and similar journals

and

2) because it says "spooky action at a distance must be accepted as a fact of nature"

In what way does that support your claim of spooky action at a distance? None whatsoever.

Couldn't agree more. That study does not support my claim about spooky action at a distance. Instead, it starts out with by noting that this is a fact of nature.

Secondly, do you know that Einstein was wrong about spooky action at a distance, and none of those people who have carried his torch were not able to prove it?

Of course I know he was wrong. Because the reason he called it "spooky action at a distance" was because he believed it to be a main indication that quantum physics was incomplete. Clearly, such "spooky action" can't occur, so he set out trying to show this (so did Bell, actually). And it turns out that Einstein was incorrect. The "spooky actions" he referred to were first experimentally verified by Alain Aspect et al. in 1981 and 82. It's been a few years since then. So physicists have had some time to read Aspect's study once or twice. There may even have been a few other experiments just to make sure (and by "a few" I mean it would be difficult to actually count how many there are, and a lot easier to look only at experiments which have involved things like superposition states of molecules affectionally dubbed Schrödinger's kittens).

Of course, to date there is no experimental evidence of superluminal signals (at least any that is acknowledged by the physics community at large), but then again there was no experimental evidence of "spooky action at a distance" until 45+ years after EPR. Instead there were thought experiments, arguments, etc., sort of like there are for superluminal signals as we speak (not all of these are freely available unless you happen to access to ScienceDirect and similar databases):

Selleri, F. (2006). Superluminal signals and the resolution of the causal paradox. Foundations of Physics, 36(3), 443-463.

GHIRARDI, G., & ROMANO, R. (2012). On a proposal of superluminal communication. Journal of physics. A, Mathematical and theoretical, 45(23).

Weinstein, S. (2006). Superluminal signaling and relativity. Synthese, 148(2), 381-399.


Jensen, R. (2010, January). On using Greenberger‐Horne‐Zeilinger three‐particle states for superluminal communication. In AIP Conference Proceedings (Vol. 1208, p. 274).

Garber, V. (2011). Explaining quantum entanglement as interactions mediated by a new superluminal field. Physics Essays, 24(2), 175-180.

Again, none of these (and other similar papers) are widely accepted and to date (so far as I know) there has not been any experimental realization of superluminal signals.



EDIT: I almost forgot. The transition from the "idealized" isolated systems in early quantum physics, when experimental designs continued to try to treat quantum systems like they had classical (i.e., let the system run, then measure) changed many terms but Einstein's description remains. For example, qubits weren't around until fairly recently (after all, von Neumann, Turing, Miller, and others who made the term "bit" popular were still explaining the term in the 1950s (e.g., The Magical Number Seven, Plus or Minus Two). Yet even here, in descriptions of methods, procedures, and current work on e.g., entanglement of atoms and qubits has held on to Einstein's famous quip:

"These oscillations result from a Ramsey-type interference process. As in the quantum memory experiment, the two pulses are applied onto two different atoms. Phase information is transferred between them by the ‘spooky action at a distance’ resulting from the quantum correlations in the EPR pair."
p. 287
Haroche, S., & Raimond, J-M. (2006). Exploring the Quantum: Atoms, Cavities and Photons (Oxford Graduate Texts). Oxford University Press

 

[Mr Spinkles]

As long as you understand that "non-locality" means there are no hidden local parameters. My initial objection was to the statement: "that these correlations must have occurred due to an instantaneous influence of one entangled particle on its distant partner." That is wrong.

What is wrong about it?*

*edit: And could you please specify whether you believe it is wrong according to standard physics as commonly understood by physicists, or based on your own personal take on things?

 

[zaybu]

The "spooky actions" he referred to were first experimentally verified by Alain Aspect et al. in 1981 and 82.

This shows you absolutely got it wrong. Aspect's experiment showed that Bell was right, and what Bell had claimed was that there are no hidden local parameters. IOW, what Einstein had claimed - spooky action at a distance - is wrong. Get it. What all this demonstrates is that quantum logic is different than classical logic.

NOTE: please refrain from posting links which you have no clue what these articles asre talking about.