EPR Paradox Failure Explained for High Schoolers

[DrChinese]

...how does Rowe's et al experiment justify application of fair sampling assumption to photon detections?
Because if you do it you get ion entanglement? But in that case I don't understand why in photon polarization experiments photons are entangled but atoms are classical and can not be entangled but in ion experiment atoms are entangled but photons are classical and can not be entangled.
Does it depend in what way we intend to interpret results of experiment?

1. Once you know fair sampling assumption is explicitly tested and supported, it can be extended elsewhere to similar tests. So we know that unfair sampling cannot be the cause of Bell test results.

2. Atoms are not classical and can be entangled.

 

[nismaratwork]

1. Once you know fair sampling assumption is explicitly tested and supported, it can be extended elsewhere to similar tests. So we know that unfair sampling cannot be the cause of Bell test results.

2. Atoms are not classical and can be entangled.

Those are the essential basics... how appropriate that your's is post "101"!

 

[ueit]

Wikipedia – Uncertainty principle
...
Published by Werner Heisenberg in 1927, the principle means that it is impossible to determine simultaneously both the position and momentum of an electron or any other particle with any great degree of accuracy or certainty. Moreover, his principle is not a statement about the limitations of a researcher's ability to measure particular quantities of a system, but it is a statement about the nature of the system itself as described by the equations of quantum mechanics.

This is not the first time when a false statement appears on Wikipedia (which is, by the way, not the direct expression of mainstream science).

In his book, "The physical principles of the quantum theory", page 20, Werner Heisenberg writes:

This formulation makes it clear that the uncertainty relation does not refer to the past; if the velocity of the electron is at first known and the position then exactly mesured, the position for times previous to the measurement may be calculated. Then for these past times Delta p x Delta q is smaller than the usual limiting value, but this knowledge of the past is of a purely speculative character, since it can never (because of the unknown change in momentum caused by the position measurement) be used as an initial condition in any calculation of the future progress of the electron ant thus cannot be subjected to experimental verification. It is a matter of personal belief whether such a calculation concerning the past hystory of the electron can be ascribed any physical reality or not

Now, in my oppinion, the simple fact that a simultaneous position and momentum can be ascribed for the past is strong evidence in favour of their physical reality. Otherwise, this fact has no explanation other than a strange coincidence. On the other hand there is a good explanation for uncertainty as a consequence of the measurement.

 

[DrChinese]

This is not the first time when a false statement appears on Wikipedia (which is, by the way, not the direct expression of mainstream science).

...

Now, in my oppinion, the simple fact that a simultaneous position and momentum can be ascribed for the past is strong evidence in favour of their physical reality. Otherwise, this fact has no explanation other than a strange coincidence. On the other hand there is a good explanation for uncertainty as a consequence of the measurement.

Everything here is basically absurd. And that is being kind.

There is NO evidence whatsoever that there is a simultaneous position and momentum for any quantum object. You can make an extrapolation as Heisenberg suggested. I can also multiply any value by any other value. So what is the physical meaning of such? Answer: none, in both cases.

As to Wikipedia, everything you say about that is wrong too. As per usual. If I wanted to get a summary of mainstream science in any area, Wikipedia would be one of my first sources. There is no better "direct expression of mainstream science" that I am aware of.

 

[DevilsAvocado]

This is not the first time when a false statement appears on Wikipedia

You have to explain why both Wikipedia & http://plato.stanford.edu/" are false.

http://plato.stanford.edu/entries/qt-uncertainty/#MinInt"
...
The same holds, mutatis mutandis, for all the other physical quantities pertaining to the system. Note that no simultaneous measurements of two or more quantities are required in defining the operational meaning of the probability distributions.

(which is, by the way, not the direct expression of mainstream science)

Okay, can you please tell us what the direct expression of mainstream science is? Don’t forget references.

Now, in my oppinion, the simple fact that a simultaneous position and momentum can be ascribed for the past is strong evidence in favour of their physical reality.

Well, that just your personal speculation, right?

My personal speculation is that physics is about making mathematical models and predictions about nature, and verify these predictions in physical experiments. If you are about to construct a CD player, using the knowledge of physics, you probably want to know in advance if the construction is working, theoretically. Not execute trial & error for a hundred years, to finally confirm that the last version worked, in retrospect...


@DrC: Agree.

 

[dx]

I would like to point out again that the EPR paradox (as far as the 'physical reality' issue is concerned), involves nothing more than what is already contained in the 'single-slit experiment' involving a single particle. As is well known, such a set up serves to illustrate that P and X cannot simultaneously enter the description of quantum phenomena, since phenomena which permit a causal analysis cannot appear in situations that permit a spacetime analysis.

Now, in the EPR experiment, we have two particles instead of one. Since [P₁ + P₂, X₁ - X₂] = 0, situations can be arranged where both X₁ - X₂ and P₁ + P₂ are meaningful. Now, a measurement of X₁ will fix X₂, and a measurement of P₁ will fix P₂, but such measurements demand mutually exclusive experimental arrangements since X₁ and P₁ do not commute. This is what Bohr is referring to in this passage:

"The wording of the above mentioned criterion ... contains an ambiguity as regards the meaning of the expression "without in any way disturbing a system". Of course, there is in a case like that just considered no question of a mechanical disturbance of the system during the last critical stage of the measuring procedure. But even at this stage, there is essentially the question of an influence on the very conditions which define the possible types of predictions regarding the future behavior of the system..."

 

[ueit]

Everything here is basically absurd. And that is being kind.

There is NO evidence whatsoever that there is a simultaneous position and momentum for any quantum object. You can make an extrapolation as Heisenberg suggested. I can also multiply any value by any other value. So what is the physical meaning of such? Answer: none, in both cases.

As to Wikipedia, everything you say about that is wrong too. As per usual. If I wanted to get a summary of mainstream science in any area, Wikipedia would be one of my first sources. There is no better "direct expression of mainstream science" that I am aware of.

Heisenberg said there is a matter of belief if a particle has a simultaneous position and momentum. The wiki article sais otherwise. I prefer to believe the man who discovered the HUP and got a Nobel price in the field over a net source where anyone, even those without a degree in the field, can edit.

The fact that you use wiki as your main source for "mainstream science", does not prove anything at all. It explains however your supperficial understanding of physics.

 

[DrChinese]

The fact that you use wiki as your main source for "mainstream science", does not prove anything at all. It explains however your supperficial understanding of physics.

Gosh, that really hertz. Guess I'll go back to my supper.

 

[ueit]

You have to explain why both Wikipedia & http://plato.stanford.edu/" are false.

Stanford Encyclopedia does not say the same thing as wiki and it does not contradict what I have said.

Okay, can you please tell us what the direct expression of mainstream science is? Don’t forget references.

The oppinion of the great names in the field, in this example Heisenberg himself. I don't understand what references would you expect for this.

Well, that just your personal speculation, right?

It is my interpretation of the available data. The particle goes from a place to another. The assumption that it has a trajectory is natural. Do you have another explanation that is more natural, or has more experimental evidence in its favour?

My personal speculation is that physics is about making mathematical models and predictions about nature, and verify these predictions in physical experiments. If you are about to construct a CD player, using the knowledge of physics, you probably want to know in advance if the construction is working, theoretically. Not execute trial & error for a hundred years, to finally confirm that the last version worked, in retrospect...

I agree with you but unfortunately QM in its standard interpretation does not offer us a model about the world, it does not describe the evolution of a system in our 3D+ time universe. It is a black-box that gives very good predictions, but still a black-box. Therefore one is free to chose a model as long as it does not contradict the QM formalism. In this case, the particle having a trajectory is not in conflict with any of QM postulates and experiments, as Heisenberg himself pointed out.

I wouldn't engage here in a debate about the phylosophy of science but I would say that explanations of past data is as scientiffic as the predictions of the future. This is the case of cosmology (Big-Bang-theory), paleonthology, and others.

 

[DrChinese]

The oppinion of the great names in the field, in this example Heisenberg himself. I don't understand what references would you expect for this.

Generally, people's opinions are not considered references - even Einstein's. Heisenberg's statement is simply a comment to the effect that there is no evidence in favor of one side or the other. I believe you will find that was said long before Bell. Possibly around the time of EPR even. So it is not really relevant, which is par for you. Please, continue to bob and weave to try to deceive those who come here to learn something.

For those who actually come here to learn something: Wiki is a great source of background on physics. Then come here to PhysicsForums to gain additional understanding and ask specific questions. When you get further along, try arxiv.org to search raw research materials.

 

[DevilsAvocado]

Stanford Encyclopedia does not say the same thing as wiki and it does not contradict what I have said.

Read again.

The oppinion of the great names in the field, in this example Heisenberg himself. I don't understand what references would you expect for this.

Heisenberg is not saying what you are saying. Reference please.

It is my interpretation of the available data. The particle goes from a place to another. The assumption that it has a trajectory is natural. Do you have another explanation that is more natural, or has more experimental evidence in its favour?

Who says QM has to be natural according to your preferences?

I agree with you but unfortunately QM in its standard interpretation does not offer us a model about the world, it does not describe the evolution of a system in our 3D+ time universe. It is a black-box that gives very good predictions, but still a black-box. Therefore one is free to chose a model as long as it does not contradict the QM formalism. In this case, the particle having a trajectory is not in conflict with any of QM postulates and experiments, as Heisenberg himself pointed out.

Chose any model you want, like http://en.wikipedia.org/wiki/Quantum_mysticism" , but please don’t call it "mainstream science".

 

[ueit]

Generally, people's opinions are not considered references - even Einstein's. Heisenberg's statement is simply a comment to the effect that there is no evidence in favor of one side or the other. I believe you will find that was said long before Bell. Possibly around the time of EPR even. So it is not really relevant, which is par for you. Please, continue to bob and weave to try to deceive those who come here to learn something.

For those who actually come here to learn something: Wiki is a great source of background on physics. Then come here to PhysicsForums to gain additional understanding and ask specific questions. When you get further along, try arxiv.org to search raw research materials.

Well, I let those "who actually come here to learn something" to choose if they want to believe you or some quasi anonimous source on wikipedia or the oppinion of a Nobel price laureate in QM.

Anyway, the wiki statement that HUP "is not a statement about the limitations of a researcher's ability to measure particular quantities of a system, but it is a statement about the nature of the system itself as described by the equations of quantum mechanics" is clearly wrong and it has been proven so by the very existence of Bohm's interpretation.

The fact that you know about Bohm's interpretation (as proven by your debates on this forum) but still support the wikipedia claim, recommends you as a prime deciever.

 

[nismaratwork]

Well, I let those "who actually come here to learn something" to choose if they want to believe you or some quasi anonimous source on wikipedia or the oppinion of a Nobel price laureate in QM.

Anyway, the wiki statement that HUP "is not a statement about the limitations of a researcher's ability to measure particular quantities of a system, but it is a statement about the nature of the system itself as described by the equations of quantum mechanics" is clearly wrong and it has been proven so by the very existence of Bohm's interpretation.

The fact that you know about Bohm's interpretation (as proven by your debates on this forum) but still support the wikipedia claim, recommends you as a prime deciever.

Newton was a brilliant man, but quoting his views on gravity don't really hold water here... I'd rather have a contemporary account of the science than the words of a brilliant man from an irrelevant time. Insulting Dr. C just makes you look weak... he's proven his knowledge in this area dozens of times over. Make an argument from REAL evidence or have the grace to be silent.

 

[ueit]

Read again.

wiki sais HUP does not allow simultaneous position and momentum ("is a statement about the nature of the system itself")
Stanford sais "no simultaneous measurements of two or more quantities are required"

There is a difference between being impossible and not being required. Here, Stanford Encyclopedia of Philosophy should help you.

Heisenberg is not saying what you are saying. Reference please.

Heisenberg sais that you are wrong.

 

[DevilsAvocado]

E o d

 

[ueit]

Newton was a brilliant man, but quoting his views on gravity don't really hold water here... I'd rather have a contemporary account of the science than the words of a brilliant man from an irrelevant time.

Newton's gravity has been replaced by Einstein's GR. HUP didn't change a bit since Heisenberg discovered it. Your analogy is therefore false.

 

[nismaratwork]

wiki sais HUP does not allow simultaneous position and momentum ("is a statement about the nature of the system itself")
Stanford sais "no simultaneous measurements of two or more quantities are required"

There is a difference between being impossible and not being required. Here, Stanford Encyclopedia of Philosophy should help you.



Heisenberg sais that you are wrong.

Heisenberg is a dead Nazi, cite your references or just let it go.

 

[nismaratwork]

Newton's gravity has been replaced by Einstein's GR. HUP didn't change a bit since Heisenberg discovered it. Your analogy is therefore false.

That was NOT my analogy. My analogy is that you can't quote people who died before a modern age of progress occurred, and call that a reference. You're not acting in the spirit of PF guidelines here, and it sounds like you're spouting nonsense.

 

[jtbell]

Closed pending cleanup.