Aspect's Experiment Was Flawed

[vanesch]

Maestro, you're not alone in finding QM "hard to swallow". QM is hard to accept. Most people who study QM seem to come to a point where they simply admit they can't wrap their brains around it. And I think the theorists have completely given up, except, of course, for the metaphysical nutjobs.

QM is certainly counter intuitive, and there are still open questions left. To me, the most important one is the measurement problem. But the difficulties in QM lead to an understanding of the difficulties in classical mechanics. Do you find that Newton's gravity *explains* things ? Can you say *why* one has to divide the other mass by the distance squared, and this somehow equals the second derivative of the position ?

cheers,
Patrick.

 

[ZapperZ]

QM is certainly counter intuitive, and there are still open questions left. To me, the most important one is the measurement problem. But the difficulties in QM lead to an understanding of the difficulties in classical mechanics. Do you find that Newton's gravity *explains* things ? Can you say *why* one has to divide the other mass by the distance squared, and this somehow equals the second derivative of the position ?

cheers,
Patrick.

I can even add to that one. Classical theories are full of "fields". No explanation on what it is, it's just... THERE! It explains ZERO mechanism on the type of interactions that a charged particle experience in such a field. All it says is "if you put q there in a field of V, then you get so and so...".

People don't find this "mysterious" because we deal with such things often. It is a "common" concept. They don't realize that these too are full of holes. Yet, this is nothing better nor worse than the same method done in QM.

I always tell people that you are NOT born with your current intuition. Your intuition is based on your accumulated knowledge. If you haven't stuidied QM, OF COURSE you find it intuitively difficult. But try doing a number of experiments. Try looking closely at what it is that you are measuring when you try to determine the position of something - what did you take for granted in doing that? You will soon realize that classical physics is more of a facade, the very same way that people think the sky is the blue ceiling when they look up on a clear, sunny day.

I can bring out many examples of simple, everyday observations in which, if I were to describe to you, are not "intuitively" obvious. It is only after I explain to you why such things happen will it become "intuitively obvious". Thus, your intuition changes with knowledge! What you found difficult to accept before, now becomes clearly obvious.

Zz.

 

[Nereid]

Don't tell them in all gory detail

cheers,
Patrick.

Well, at least I didn't start to tell the neutrino story, or tectonic plates, or snowball Earth, or the distance scale of the universe, ...

In the sense of having a relatively smooth path from theory to good experimental consistency and validation, QM had an easy ride.

Perhaps I should start a thread called 'unfinished symphonies'?

 

[ZapperZ]

In the sense of having a relatively smooth path from theory to good experimental consistency and validation, QM had an easy ride.

I'm not so sure about that. Like any new and revolutionary theory, QM had many obstacles to over come, as should anything new. The founding fathers certainly didn't get honored for their work till quite late. See

http://physicsweb.org/article/world/15/8/7/1

Zz.

 

[Nereid]

To be sure Zapper, new stuff is always a struggle, and something as radical as QM certainly had its challenges! My rule of thumb is it takes at least a decade for something new to get sufficient experimental and theoretical oomph (a point I keep emphasising re dark energy (and other areas in astrophysics and cosmology); to my taste far too many people are rushing off to their PR departments with marketing fluff that glosses over the decade or more of work that has to be done yet before anything halfway decent can be established).

QM had lots of experimental validation, fairly quickly (measured on timescales of decades), and from many different directions; to be sure many aspects had to wait many decades for experiments to shed light on the theory (so to speak) - e.g. Aspect.

Can we agree that in real science Patrick's summary is perhaps just a tad too high level?

 

[DrChinese]

My rule of thumb is it takes at least a decade for something new to get sufficient experimental and theoretical oomph (a point I keep emphasising re dark energy (and other areas in astrophysics and cosmology);

A decade seems about right to me too. Funny that for all the old stuff (SR, QM), a decade is just a blip. For new theory (dark energy, currently inflating universe, or whatever), a decade seems like an eternity and the progress appears negligible.

But it won't in retrospect. Why, even Aspect is old hat now! That was over 2 decades ago...

 

[vanesch]

Can we agree that in real science Patrick's summary is perhaps just a tad too high level?

Sure, I was cutting corners !
But I had the idea, maybe wrongly, that Maestro claimed that the predictions of Newton were correct, and that Einstein, just for the sake of it, changed everything to relativity in order to provide deeper understanding , and not for the sake of better experimental succes. I guess he is thinking that both make the same predictions.

And if you want to talk about real, real science, there's a lot of sociological considerations too ! (these were the "gory details" I was referring to).

cheers,
Ptrick.

 

[ZapperZ]

To be sure Zapper, new stuff is always a struggle, and something as radical as QM certainly had its challenges! My rule of thumb is it takes at least a decade for something new to get sufficient experimental and theoretical oomph (a point I keep emphasising re dark energy (and other areas in astrophysics and cosmology); to my taste far too many people are rushing off to their PR departments with marketing fluff that glosses over the decade or more of work that has to be done yet before anything halfway decent can be established).

My rule of thumb has been that theory needs a longer "gestation" period than experimental observation. It takes a theory at LEAST 10 years (on par with your decade) of continuous testing and prodding for it to be widely accepted to be valid. This of course, assumes that the theory makes testable predictions, which totally disqualifies String, Superstring, M-Theory. Experimental observations, on the other hand, only require that another independent group reporting a consistent observation. Thus, monumentous discovery such as the high-Tc superconductor, only required a 1-year period between discovery and complete chaos! :)

And I totally agree with you about people rushing to publicize their work, even way before those things appear in a peer-review journal. One would think we would all have learned a lesson from the Fleishmann-Pons debacle.

QM had lots of experimental validation, fairly quickly (measured on timescales of decades), and from many different directions; to be sure many aspects had to wait many decades for experiments to shed light on the theory (so to speak) - e.g. Aspect.

Can we agree that in real science Patrick's summary is perhaps just a tad too high level?

I think both situations are valid, and there are enough examples in each. I can also bring in other types of situations where there are only qualitative, not quantitative, agreements in the beginning. So the path towards acceptance can be many (much like all the possible paths in a Feyman path integral). In the end, a large collection of experimental results are the only means to filter out what theoretical description is valid.

This last point is what I think a lot of people outside of physics do not fully appreciate. A single theory does not make a single, or even a small number of predictions. The BCS theory of superconductivity, for example, make a whole slew of predictions/consequences, ranging from the energy gap in the density of states (tested via tunneling experiments), superfluid density (from optical conductivity experiments), Meissner effect (via magnetic susceptibility measurement), etc, etc... A good theory must be consistent with A LOT of results from various kinds of experiments. This is because physics is inter-related - it isn't just a set of disjointed, unconnected collection of information. You can't pull something out in one corner and not expect something else in a totally different area to be affected. So when people claim to have some wild "theory" of something, they seem to forget about a slew of experimental observations that they need to be consistent with.

With this in mind, there is one impressive fact that can never be overemphasized. Considering the unbelievably huge area of application and testability of QM, ranging from particle physics to atomic/nuclear physics, to the very material we all use everyday, there hasn't been even ONE experimental evidence that is inconsistent with QM! ZILCH! I mean, think about it! If this isn't astounding to you, then you haven't learned enough physics. It is not without any weight that during the centenial celebration of QM in 1999, physicists almost unanimously declared that QM is the most successful physical theory so far in the history of human civilization.

Zz.

 

[ZapperZ]

And if you want to talk about real, real science, there's a lot of sociological considerations too ! (these were the "gory details" I was referring to).

cheers,
Ptrick.

Of course there are, but only with respect to what areas to pursue and how easy (or difficult) it is to pursue them. Sociological considerations have no bearings on the validity of physics ideas, at least not for long. So this is in contradictions to the post-modernists claim that all of science and scientific ideas are social constructions. No matter how much money is poured into something, or how much social and political pressure there is to accept something, if something is invalid, it remains invalid.

Zz.

 

[Ontoplankton]

Speaking of broken records, there exists a fully local, deterministic, and in a sense realistic interpretation of QM that everyone agrees is compatible with Aspect's results. Learning of it may reduce your desire to reject quantum mechanics itself (which you shouldn't do; it works perfectly well).

And speaking of sociological considerations, I'm beginning to wonder if there isn't some sort of cognitive dissonance effect at work: if it turns out QM makes good sense after all, then all those six impossible things people forced themselves to believe before breakfast were needless effort. ;)

 

[vanesch]

So this is in contradictions to the post-modernists claim that all of science and scientific ideas are social constructions.

Sure, didn't want to indicate this at all, I also have a post-modernist for breakfast each morning :-) I was more thinking of new ideas being favored by big boys to emerge easier than those being not liked. But it is just a matter of, well, a generation at most. A concrete example is probably Chandrasekar and his black hole formation.

cheers,
Patrick.

 

[vanesch]

Speaking of broken records, there exists a fully local, deterministic, and in a sense realistic interpretation of QM that everyone agrees is compatible with Aspect's results. Learning of it may reduce your desire to reject quantum mechanics itself (which you shouldn't do; it works perfectly well).

Care to discuss a bit Many-worlds ? I know about it, but not in all the details, so questions remain.
I'll start a new thread for it.

cheers,
Patrick.

 

[kurious]

I would like to see Aspect's experiment and other entanglement experiments done
in a much weaker gravitational field _perhaps deep inside the Earth or in space -
in order to see if gravity has any effect on the outcome.Physicists will say gravity has nothing to do with it but shouldn't this be tested experimentally.

 

[metacristi]

The problem regarding the sensibility of detectors ceased to be considered a serious problem though some doubts still remain.It's interesting to note however that there are other objections which are principially unsolvable,based only on empirical evidence.

The first is that in interpreting the results of Aspect's experiment we have to reside on logic,namely on modus tollens.From the empirical observation that Bell's inequalities are violated we deduce that one of the premises is false.In this case we have two main choices:either deny the principle of realism altoghether (by denying the existence of hidden variables altoghether,meaning also intrinsic indeterminism) as copenhagenists do or deny only the principle of locality (this is the minimal case).There is however another possibility namely denying that logic is a valid way of reasoning about natural facts,in this case at least!Of course there is no good reason to think that the traditional hypothetico-deductive method does not work here (it had a tremendous success before) so no scientist will be too much bothered by this problem.Still this let the door open to skepticism,basically there is no way to refute it in a clear way.We have the right however to prefer rationally the stance that modus tollens is a valid way of reasoning,there are more logical reasons supporting it.

The second,much more serious one,is that Bell's assumes,intrinsically,in the premises the principle of free choice,namely that experiencers have free will,the measuring angles are free variables.As even Bell recognize '...if our measurements are not independently variable as we supposed...even if chosen by apparently free-willed physicists... then Einstein local causality can survive...apparently separate parts of the world become deeply entangled, and our apparent free will is entangled with them.'Thus the meaning of Bell's inequalities violation is not so clear cut in spite of the fact that majority of scientists prefer to consider Aspect's experiment as ruling out at least the principle of locality.

 

[kurious]

The energy associated with gravitational field is small compared to other fields like EM
but it takes little or no energy to change the polarization of a photon.

 

[ZapperZ]

The problem regarding the sensibility of detectors ceased to be considered a serious problem though some doubts still remain.It's interesting to note however that there are other objections which are principially unsolvable,based only on empirical evidence.

The first is that in interpreting the results of Aspect's experiment we have to reside on logic,namely on modus tollens.From the empirical observation that Bell's inequalities are violated we deduce that one of the premises is false.In this case we have two main choices:either deny the principle of realism altoghether (by denying the existence of hidden variables altoghether,meaning also intrinsic indeterminism) as copenhagenists do or deny only the principle of locality (this is the minimal case).There is however another possibility namely denying that logic is a valid way of reasoning about natural facts,in this case at least!Of course there is no good reason to think that the traditional hypothetico-deductive method does not work here (it had a tremendous success before) so no scientist will be too much bothered by this problem.Still this let the door open to skepticism,basically there is no way to refute it in a clear way.We have the right however to prefer rationally the stance that modus tollens is a valid way of reasoning,there are more logical reasons supporting it.

The second,much more serious one,is that Bell's assumes,intrinsically,in the premises the principle of free choice,namely that experiencers have free will,the measuring angles are free variables.As even Bell recognize '...if our measurements are not independently variable as we supposed...even if chosen by apparently free-willed physicists... then Einstein local causality can survive...apparently separate parts of the world become deeply entangled, and our apparent free will is entangled with them.'Thus the meaning of Bell's inequalities violation is not so clear cut in spite of the fact that majority of scientists prefer to consider Aspect's experiment as ruling out at least the principle of locality.

Let's be clear on one thing here: if we have a photon detector with 100% efficiency, we won't be having most these kinds of questions anymore. A lot of issues surrounding the possible loopholes surrounding the interpretations of EPR-type of experiments hinges on the ability to detect the coincidences at both detectors.

Secondly, we seem to be ignoring a stricter, and clearer variation of Bell's theorem. I am pretty sure that the CHSH scheme has address some, if not all, of the issues you have brought up.[1] Practically all of the latter-day EPR-type experiments test for violation of the CHSH scheme. However, at some point, this becomes a question of semantics, and what we mean exactly by "local realism" and "non-local hidden variables", etc. I think that may belong in a separate string by itself (not that we haven't had several already during the previous months).

Zz.

[1] J.F. Clauser et al., Phys. Rev. Lett. v.23, p.880 (1969).

 

[ZapperZ]

Just in time for all the fun and excitement, Travis Norsen posted a paper titled "EPR and Bell Locality" on arXiv appearing today (well, late yesterday evening, to be precise). Have a look at it. At the very least, you will have a good set of references from it.

http://arxiv.org/abs/quant-ph/0408105

Zz.

 

[DrChinese]

1. The first is that in interpreting the results of Aspect's experiment we have to reside on logic,namely on modus tollens.From the empirical observation that Bell's inequalities are violated we deduce that one of the premises is false.In this case we have two main choices:either deny the principle of realism altoghether (by denying the existence of hidden variables altoghether,meaning also intrinsic indeterminism) as copenhagenists do or deny only the principle of locality (this is the minimal case).There is however another possibility namely denying that logic is a valid way of reasoning about natural facts,in this case at least!Of course there is no good reason to think that the traditional hypothetico-deductive method does not work here (it had a tremendous success before) so no scientist will be too much bothered by this problem.Still this let the door open to skepticism,basically there is no way to refute it in a clear way.We have the right however to prefer rationally the stance that modus tollens is a valid way of reasoning,there are more logical reasons supporting it.

2. The second,much more serious one,is that Bell's assumes,intrinsically,in the premises the principle of free choice,namely that experiencers have free will,the measuring angles are free variables.As even Bell recognize '...if our measurements are not independently variable as we supposed...even if chosen by apparently free-willed physicists... then Einstein local causality can survive...apparently separate parts of the world become deeply entangled, and our apparent free will is entangled with them.'Thus the meaning of Bell's inequalities violation is not so clear cut in spite of the fact that majority of scientists prefer to consider Aspect's experiment as ruling out at least the principle of locality.

Semantics does figure into the equation here. Accepting Aspect (as I do) implies that either reality or locality must be rejected. Tying to your comments:

1. Reality rejected: I think it would be reasonable to conclude that reality is rejected if logic does not hold. That is certainly in the flavor of what EPR was getting at. Although later writers have tried to split hairs over the words, EPR had simpler roots. I do not think the authors of EPR would have taken refuge in criticisms of EPR experiments by raising the "fair sampling" criticism or by stating that logic might not hold true at the quantum level (even though they could acknowledge such possibility).

2. There is more than one way to violate locality. Exceeding c is not the only way. Another route is that the future can affect the past. c could still be respected and locality violated because the time for a cause/effect to traverse a distance is in effect negative from the reference of an observer moving forward in time, which seems to be faster than c. In such a scenario, the "free choice" you describe is not truly "after the fact" in all reference frames. I would call this a violation of locality, but some might not see it that way.

The Bell Theorem is plenty strong, and certainly accomplishes primary objective #1: to limit competing theories to QM. It sets a major hurdle, although it does not eliminate all future competitors. If anyone proposes a classical local realistic theory, you know without further consideration it is wrong and will not be useful.

 

[metacristi]

Let's be clear on one thing here: if we have a photon detector with 100% efficiency, we won't be having most these kinds of questions anymore. A lot of issues surrounding the possible loopholes surrounding the interpretations of EPR-type of experiments hinges on the ability to detect the coincidences at both detectors.

Secondly, we seem to be ignoring a stricter, and clearer variation of Bell's theorem. I am pretty sure that the CHSH scheme has address some, if not all, of the issues you have brought up.[1] Practically all of the latter-day EPR-type experiments test for violation of the CHSH scheme. However, at some point, this becomes a question of semantics, and what we mean exactly by "local realism" and "non-local hidden variables", etc. I think that may belong in a separate string by itself (not that we haven't had several already during the previous months).

Zz.

[1] J.F. Clauser et al., Phys. Rev. Lett. v.23, p.880 (1969).

We haven't escaped of all problems yet,even using observables other than spin.As far as I know the last such experiment,using ions,is not considered as compeling because they were not enough separated in space.So mere skepticism is still rational.Anyway since establishing a standard of knowledge (openly accepted as fallible) does not involve absolute truth I consider the current evidence as representing a sufficient reason to support the rejection of local hidden variables.If some compelling data against will ever appear,way beyond a mere skepticism,counting as sufficient reasons,science will (re)accept the principle of locality.However this does not mean we are deceived now in accepting provisionally the rejection of locality as knowledge.

As regarding the validity of modus ponens,well the problem is much more complicated.We have no proof that logic should apply with necessity to natural facts,even if a conclusion were unique and unavoidable logically,deduced from true premises.Likewise with the modus tollens when applied in this case (the premises are fallible).Even if we had 100% empirical certainty that Bell's inequalities are violated (more generally all such types of equalities,even those involving single detection) we still need to assume the validity of the modus tollens scheme as applying to nature in order to accept that one of the premises is false.For example some might argue that logic does not apply here to nature,that is even if we are compelled to think (as logic indicates) that one premise is false this does not mean also that ontologically this must be the case.Basically there is no way to avoid this on empirical grounds entirely but,as I've pointed before,we have enough reasons to prefer that logic is a valid 'tool' even here.

 

[metacristi]

Semantics does figure into the equation here. Accepting Aspect (as I do) implies that either reality or locality must be rejected. Tying to your comments:

1. Reality rejected: I think it would be reasonable to conclude that reality is rejected if logic does not hold. That is certainly in the flavor of what EPR was getting at. Although later writers have tried to split hairs over the words, EPR had simpler roots. I do not think the authors of EPR would have taken refuge in criticisms of EPR experiments by raising the "fair sampling" criticism or by stating that logic might not hold true at the quantum level (even though they could acknowledge such possibility).

2. There is more than one way to violate locality. Exceeding c is not the only way. Another route is that the future can affect the past. c could still be respected and locality violated because the time for a cause/effect to traverse a distance is in effect negative from the reference of an observer moving forward in time, which seems to be faster than c. In such a scenario, the "free choice" you describe is not truly "after the fact" in all reference frames. I would call this a violation of locality, but some might not see it that way.

The Bell Theorem is plenty strong, and certainly accomplishes primary objective #1: to limit competing theories to QM. It sets a major hurdle, although it does not eliminate all future competitors. If anyone proposes a classical local realistic theory, you know without further consideration it is wrong and will not be useful.

Well certainly the Bell's theorem is strong,there is enough evidence for this but skpeticism (without any 'positive' claims) is still rational.Interesting the points you made at 2.I still have to think at all the implications of future affecting the past to the 'free will' assumption (had you in mind the transactional interpretation?) considered by many one of the strongest objection to the rejection of locality (at least).In all case this objection is enough strong to cool down those who claim that we [have] almost certitudes (if not certitudes) that local hidden variables theories are impossible.

 

[Nereid]

We haven't escaped of problems yet,even using observables other than spin.As far as I know the last such experiment,using ions,is not considered as compeling because they were not enough separated in space.So mere skepticism is still rational.Anyway since establishing a standard of knowledge (openly accepted as fallible) does not involve absolute truth I consider the current evidence as representing a sufficient reason to support the rejection of local hidden variables.If some compelling data against will ever appear,way beyond a mere skepticism,counting as sufficient reasons,science will (re)accept the principle of locality.However this does not mean we are deceived now in accepting provisionally the rejection of locality as knowledge.

As regarding the validity of modus ponens,well the problem is much more complicated.We have no proof that logic should apply with necessity to natural facts,even if a conclusion were unique and unavoidable logically,deduced from true premises.Likewise with the modus tollens when applied in this case (the premises are fallible).Even if we had 100% empirical certainty that Bell's inequalities are violated (more generally all such types of equalities,even those involving single detection) we still need to assume the validity of the modus tollens scheme as applying to nature in order to accept that one of the premises is false.For example some might argue that logic does not apply here to nature,that is even if we are compelled to think (as logic indicates) that one premise is false this does not mean also that ontologically this must be the case.Basically there is no way to avoid this on empirical grounds entirely but,as I've pointed before,we have enough reasons to prefer that logic is a valid 'tool' even here.

One small () challenge with re-evaluating logic is the need to construct descriptions/explanations/(whatever they would be called in the 'new logic') for everything that has been shown to be consistent with the current theories (QM, GR, etc). If there were some 'smooth transition at the limit', so outside its main domain of applicability, the new logic worked just like that embedded in QM etc, it may not be so challenging. However, just my personal guess, any 'new logic' would require pretty much a complete re-write of all of physics ... not a job for the faint-hearted!

 

[metacristi]

One small () challenge with re-evaluating logic is the need to construct descriptions/explanations/(whatever they would be called in the 'new logic') for everything that has been shown to be consistent with the current theories (QM, GR, etc). If there were some 'smooth transition at the limit', so outside its main domain of applicability, the new logic worked just like that embedded in QM etc, it may not be so challenging. However, just my personal guess, any 'new logic' would require pretty much a complete re-write of all of physics ... not a job for the faint-hearted!

I tend to agree with you,especially that the new logics would require a broad rethinking of all physics.Anyway,from what I've read,physicists and philosophers of science reduced substantially their initial interest in devising quantum logic(s).Omnes for example say something about the efforts of von Neuman in this direction (some axioms of classical logic are dropped) but underlie further that formal logic is enough for the interpretation of the standard formalism of QM.

 

[vanesch]

I tend to agree with you,especially that the new logics would require a broad rethinking of all physics

And all of mathematics ! That's a bigger problem, because then the toolbox for physicists is empty ! You wouldn't even have integers !

cheers,
Patrick.

 

[metacristi]

The idea with devising quantum logics appeared as a consequence of the implications of the Copenhagen interpretation of QM.Some logic formulas,valid under formal logic,seemed to be violated when applied to the quantum world so it seemed that we need a new,non boolean logic.Probably from here stemed (also) the Putnam-Quine thesis that mathematics and logic can be revised in the light of new empirical evidence.

The problem with this approach is that it is presupposed too much in the premises,namely the validity only of copenhagen interpretation.Or,it is well known,both 'weak' interpretation of Heisenberg's uncertainty principle and the 'pilot-wave' hypothesis are [also] equally valid,on empirical grounds,thus interpreting observed facts (namely the two slits experiment and so on) do not really require devising new logics with necessity.Anyway today it is much more widespread the approach,even amongst copenhagenists,that we do not need a new quantum logic,algebraic systems are enough to formulate quantum mechanics.From what I've read Omnes is in line with this by requiring that the axioms of any quantum logic be consistent with those of formal logic.

Finally it is interesting to note here that even Quine renounced later at his own thesis by arguing that quantum logics are not replacements of formal logic.

 

[Nereid]

The idea with devising quantum logics appeared as a consequence of the implications of the Copenhagen interpretation of QM.Some logic formulas,valid under formal logic,seemed to be violated when applied to the quantum world so it seemed that we need a new,non boolean logic.Probably from here stemed (also) the Putnam-Quine thesis that mathematics and logic can be revised in the light of new empirical evidence.

The problem with this approach is that it is presupposed too much in the premises,namely the validity only of copenhagen interpretation.Or,it is well known,both 'weak' interpretation of Heisenberg's uncertainty principle and the 'pilot-wave' hypothesis are [also] equally valid,on empirical grounds,thus interpreting observed facts (namely the two slits experiment and so on) do not really require devising new logics with necessity.Anyway today it is much more widespread the approach,even amongst copenhagenists,that we do not need a new quantum logic,algebraic systems are enough to formulate quantum mechanics.From what I've read Omnes is in line with this by requiring that the axioms of any quantum logic be consistent with those of formal logic.

Finally it is interesting to note here that even Quine renounced later at his own thesis by arguing that quantum logics are not replacements of formal logic.

Whew! That reduces the scope of the program enormously - 'simply' show that the maths which physicists use (well, strictly, just that used in the relevant parts of QM) is fully consistent with formal logic .. you know, do a 'meta-Whitehead/Russell'. Piece of cake, unless it's a program that's already all but complete, shouldn't take more than, oh, a century or two

 

[danitaber]

new thread

hi. I posted a new thread about this physics logic thing. sounds interesting. I would like to learn more.

 

[meteor]

You DO know that EPR-type experiments have progressed SIGNIFICANTLY beyond the Aspect experiment, and that more accurate tests by Zeilinger & Co. have produced even more accurate confirmation of QM, don't you?

Wineland also violated Bell's inequality. The experiment was reported in an issue of Nature in 2001
Here's the paper, but requires subscription
"Experimental violation of a Bell's inequality with efficient detection"

http://www.nature.com/cgi-taf/DynaPage.taf?file=/nature/journal/v409/n6822/abs/409791a0_fs.html

 

[DrChinese]

Just in time for all the fun and excitement, Travis Norsen posted a paper titled "EPR and Bell Locality" on arXiv appearing today (well, late yesterday evening, to be precise). Have a look at it. At the very least, you will have a good set of references from it.

http://arxiv.org/abs/quant-ph/0408105

Zz.

I have looked over this paper. I think the conclusion is very controversial - that EPR and Bell combine to "prove" that it is the locality condition which must be sacrificed. In fact, I think the author's conclusion is wrong. Has anyone else looked at this in detail?

Specifically, he draws his conclusion (28) from EPR (26) and Bell (27) and I think this was unjustified for several reasons. First, it requires use of boolean logic which may or may not hold. I think I can demonstrate this error in logic.

In addition, his (27) is not a fair synopsis of the Bell formalism. He says that according to Bell: If quantum mechanics is incomplete, then it must be non-local. I think a more accurate formulation is (according to Bell): Any hidden variable theory which agrees with QM must be non-local. To me, those statements are far from equivalent. Comments?

 

[kurious]

DR Chinese:
In addition, his (27) is not a fair synopsis of the Bell formalism. He says that according to Bell: If quantum mechanics is incomplete, then it must be non-local. I think a more accurate formulation is (according to Bell): Any hidden variable theory which agrees with QM must be non-local. To me, those statements are far from equivalent. Comments?

Kurious:

Why are hidden variables non-local?

 

[DrChinese]

DR Chinese:
In addition, his (27) is not a fair synopsis of the Bell formalism. He says that according to Bell: If quantum mechanics is incomplete, then it must be non-local. I think a more accurate formulation is (according to Bell): Any hidden variable theory which agrees with QM must be non-local. To me, those statements are far from equivalent. Comments?

Kurious:

Why are hidden variables non-local?

Because Bell's Theorem rules out local hidden variable theories (if the predictions of QM are correct, as they appear to be per Aspect). The "standard" interpretation of this is that either a) locality is violated in nature; or b) there are no hidden variables. Norsen's paper says it is a) specifically.