First loophole-free Bell test?

[bohm2]

While this is the first Bell test that simultaneously addresses both the detection and the locality loophole, am I mistaken that this would still not be considered a loophole-free test?

In the past decades, numerous ingenious Bell inequality tests have been reported. However, because of experimental limitations, all experiments to date required additional assumptions to obtain a contradiction with local realism, resulting in loopholes. Here we report on a Bell experiment that is free
of any such additional assumption and thus directly tests the principles underlying Bell's inequality...Our experiment realizes the first Bell test that simultaneously addresses both the detection loophole and the locality loophole. Being free of the experimental loopholes, the setup can test local realist theories of nature without introducing extra assumptions such as fair-sampling, a limit on (sub-)luminal communication or the absence of memory in the setup.

Experimental loophole-free violation of a Bell inequality using entangled electron spins separated by 1.3 km
http://arxiv.org/pdf/1508.05949v1.pdf

“Spookiness” Confirmed by the First Loophole-free Quantum Test
http://fqxi.org/community/forum/topic/2581

 

[gill1109]

While this is the first Bell test that simultaneously addresses both the detection and the locality loophole, am I mistaken that this would still not be considered a loophole-free test?

Experimental loophole-free violation of a Bell inequality using entangled electron spins separated by 1.3 km
http://arxiv.org/pdf/1508.05949v1.pdf

“Spookiness” Confirmed by the First Loophole-free Quantum Test
http://fqxi.org/community/forum/topic/2581

It also addresses the memory loophole. As far as I can tell it addresses every loophole which is of experimental nature, ie due to the experimenter not adhering to a rigorous experimental protocol. And we have known since Bell (1981) ("Bertlmann's socks") what that protocol is. No experiment can however escape metaphysical looholes, in particular, the super-determinism (aka conspiracy) loophole. The random settings were actually determined at the time of the big-bang so the stuff in Alice's lab already knows what settings Bob is going to use. One can only try to make invocation of that loophole ludicrous. Appeal to Occam's razor.

 

[DrChinese]

It also addresses the memory loophole. As far as I can tell it addresses every loophole which is of experimental nature, ie due to the experimenter not adhering to a rigorous experimental protocol. And we have known since Bell (1981) ("Bertlmann's socks") what that protocol is. No experiment can however escape metaphysical looholes, in particular, the super-determinism (aka conspiracy) loophole. The random settings were actually determined at the time of the big-bang so the stuff in Alice's lab already knows what settings Bob is going to use. One can only try to make invocation of that loophole ludicrous. Appeal to Occam's razor.

And I see one of your papers was referenced as well.

 

[gill1109]

And I see one of your papers was referenced as well.

You bet! I am really proud of that. I have written up my story regarding this experiment at http://www.math.leidenuniv.nl/~gill/#loophole (enjoy the pictures, then follow the link to http://www.math.leidenuniv.nl/~gill/loophole.txt)

 

[stevendaryl]

So when you say all loopholes, that includes:

1. The possibility that the detections in EPR are not actually spacelike-separated.
2. The possibility that detection/non-detection is not random, but may depend on device settings.
3. The possibility that corresponding twin pairs are misidentified.
4. ?

(I don't know what the memory loophole is...)

 

[DrChinese]

(I don't know what the memory loophole is...)

http://arxiv.org/abs/quant-ph/0205016

Quantum nonlocality, Bell inequalities and the memory loophole
Jonathan Barrett, Daniel Collins, Lucien Hardy, Adrian Kent, Sandu Popescu

In the analysis of experiments designed to reveal violation of Bell-type inequalities, it is usually assumed that any hidden variables associated with the nth particle pair would be independent of measurement choices and outcomes for the first (n−1) pairs. Models which violate this assumption exploit what we call the {\it memory loophole}. We focus on the strongest type of violation, which uses the {\it 2-sided} memory loophole, in which the hidden variables for pair n can depend on the previous measurement choices and outcomes in both wings of the experiment. We show that the 2-sided memory loophole allows a systematic violation of the CHSH inequality when the data are analysed in the standard way, but cannot produce a violation if a CHSH expression depending linearly on the data is used. In the first case, the maximal CHSH violation becomes small as the number of particle pairs tested becomes large. Hence, although in principle the memory loophole implies a slight flaw in existing analyses of Bell experiments, the data still strongly confirm quantum mechanics against local hidden variables.
We consider also a related loophole, the {\it simultaneous measurement loophole}, which applies if all measurements on each side are carried out simultaneously. We show that this can increase the probability of violating the linearised CHSH inequality as well as other Bell-type inequalities.

 

[gill1109]

So when you say all loopholes, that includes:

1. The possibility that the detections in EPR are not actually spacelike-separated.
2. The possibility that detection/non-detection is not random, but may depend on device settings.
3. The possibility that corresponding twin pairs are misidentified.
4. ?

(I don't know what the memory loophole is...)

There is no detection/non-detection. There is a signal midway between Alice and Bob's laboratory that we have a pair of spins to measure. Measurement settings are chosen at random. The measurement is done, The settings and outcomes are stored. So quickly that Alice's diamond can't know Bob's settings. Read Bell (1981) "Bertlmann's socks".

 

[stevendaryl]

There is no detection/non-detection. There is a signal midway between Alice and Bob's laboratory that we have a pair of spins to measure. Measurement settings are chosen at random. The measurement is done, The settings and outcomes are stored. So quickly that Alice's diamond can't know Bob's settings. Read Bell (1981) "Bertlmann's socks".

I'm not sure that I understand your response. In the case of spin-1/2 EPR, if you have a source of twin pairs, it will occasionally happen that Alice detects one particle, but Bob fails to detect the corresponding antiparticle, or vice-versa. So you have to discard those cases when compiling your statistics.

[edit]Not to mention the possibility that neither particle is detected.

 

[stevendaryl]

I'm not sure that I understand your response. In the case of spin-1/2 EPR, if you have a source of twin pairs, it will occasionally happen that Alice detects one particle, but Bob fails to detect the corresponding antiparticle, or vice-versa. So you have to discard those cases when compiling your statistics.

This possible issue is listed in Wikipedia's list of loopholes
https://en.wikipedia.org/wiki/Looph...ents#Detection_efficiency.2C_or_fair_sampling

 

[stevendaryl]

There is no detection/non-detection. There is a signal midway between Alice and Bob's laboratory that we have a pair of spins to measure. Measurement settings are chosen at random. The measurement is done, The settings and outcomes are stored. So quickly that Alice's diamond can't know Bob's settings. Read Bell (1981) "Bertlmann's socks".

From skimming the paper, it sounds like they avoid detection failure problems as follows:

By conditioning the validity of a Bell test trial on this event-ready signal, failed entanglement distribution events are upfront excluded from being used in the Bell test.

 

[DrChinese]

I'm not sure that I understand your response. In the case of spin-1/2 EPR, if you have a source of twin pairs, it will occasionally happen that Alice detects one particle, but Bob fails to detect the corresponding antiparticle, or vice-versa. So you have to discard those cases when compiling your statistics.

[edit]Not to mention the possibility that neither particle is detected.

More of an issue with photons than electrons. With photons you also have the coincidence time window issue which is closely related. Such could account for a more appreciable portion of the total events. You don't really have that with electrons in these experiments.

 

[stevendaryl]

More of an issue with photons than electrons. With photons you also have the coincidence time window issue which is closely related. Such could account for a more appreciable portion of the total events. You don't really have that with electrons in these experiments.

Are you saying that every electron produced is eventually detected? (Or a sizable enough fraction of them?)

 

[bohm2]

This experiment has also got some press in Nature:

“It is a truly ingenious and beautiful experiment,” says Anton Zeilinger, a quantum physicist at the University of Vienna. “I wouldn’t be surprised if in the next few years we see one of the authors of this paper, along with some of the older experiments, Aspect’s and others, named on a Nobel Prize,” says Matthew Leifer, a quantum physicist at the Perimeter Institute in Waterloo, Ontario. “It’s that exciting.”

Quantum 'spookiness' passes toughest test yet
http://www.nature.com/news/quantum-spookiness-passes-toughest-test-yet-1.18255

 

[DirkMan]

They clearly talk in the paper about the "free will" condition, locality loophole and the fair sampling loophole.

What I can infer from this experiment is that previous Bell experimenters , had as much "free will" as a quantum random number generator.

 

[zonde]

Are you saying that every electron produced is eventually detected? (Or a sizable enough fraction of them?)

They don't produce electrons in this experiment. They say: "The boxes at location A and B each contain a single NV centre electron spin in diamond."
So it's peace of diamond with "NV centre" (don't know what it is).
So the "particles" are always there. However they are not always entangled. They produce photons from these NV centers and perform entanglement swapping. Bell state measurement rarely gives required output. But this measurement happens independently from basis selection and basis dependent measurement so that fair sampling loophole does not apply.

 

[gill1109]

The experiment is performed exactly following the rigorous protocol of Bell (1981) "Bertlmann's socks". See figure 6 from that paper below. The "experimental unit" is not a pair of particles. Forget the word particle, forget the word wave. The experimental unit is a time-slot. At two distant locations, at the beginning of the time-slot, Alice and Bob each toss coins, switch a button on a machine according to H or T, and then observe an outcome +/-1.

http://www.math.leidenuniv.nl/~gill/#loophole (look at pictures and follow link to http://www.math.leidenuniv.nl/~gill/loophole.txt)

See also

http://www.slideshare.net/gill1109/epidemiology-meets-quantum-statistics-causality-and-bells-theorem

 

[f95toli]

More of an issue with photons than electrons. With photons you also have the coincidence time window issue which is closely related. Such could account for a more appreciable portion of the total events. You don't really have that with electrons in these experiments.

The experiments uses NV centres in diamond but the entanglement is still mediated by optical photons in a fibre. The reason NV centres are used in this type of experiment is that they can have very long coherence times and can be relatively easily be manipulated using microwave control pulses (NV centres have both optical and microwave transitions); they can also be read-out with very high fidelity.

I saw a talk by one of the authors of this paper almost exactly a year ago. He was then very confident that they would be able to do this. I am glad he was right

 

[harrylin]

While this is the first Bell test that simultaneously addresses both the detection and the locality loophole, am I mistaken that this would still not be considered a loophole-free test?

Experimental loophole-free violation of a Bell inequality using entangled electron spins separated by 1.3 km
http://arxiv.org/pdf/1508.05949v1.pdf

“Spookiness” Confirmed by the First Loophole-free Quantum Test
http://fqxi.org/community/forum/topic/2581

That is very interesting - even extremely interesting!
Concerning "loophole-free", it very much depends on the kind of loopholes one considers. In particular, their claim that:

"Our observation of a loophole-free Bell inequality violation thus rules out all local realist theories that accept that the number generators timely produce a free random bit and that the outputs are final once recorded in the electronics" ,

can IMHO not be correct for the following reason. What is often overlooked or forgotten, is that an important possible theoretical loophole was created by Bell right at the start of his derivation. According to Jaynes (and I'm not aware that this was ever challenged), Bell's formula which was meant to just impose "no action at a distance", is technically wrong; unspecified additional assumptions are needed to make it right. Jaynes commented:

"Thus while the QM formalism disagrees with Bell's factorization (14), it appears consistent with what we have called the "fundamentally correct" probability relations [..] . Recognizing this, it is evident that one could produce any number of experimental tests where the predictions of QM conflict with various predictions of (14)." - Jaynes, in "Clearing up mysteries - the original goal"

As that discussion dates far back, it is unlikely that that loophole will ever be closed. Instead, and especially if indeed experimental loopholes are closed to the satisfaction of most, it could be the clue to better insight about "spookiness" which might be not that "spooky" after all.

 

[gill1109]

That is very interesting - even extremely interesting!
Concerning "loophole-free", it very much depends on the kind of loopholes one considers. In particular, their claim that:

"Our observation of a loophole-free Bell inequality violation thus rules out all local realist theories that accept that the number generators timely produce a free random bit and that the outputs are final once recorded in the electronics" ,

can IMHO not be correct for the following reason. What is often overlooked or forgotten, is that an important possible theoretical loophole was created by Bell right at the start of his derivation. According to Jaynes (and I'm not aware that this was ever challenged), Bell's formula which was meant to just impose "no action at a distance", is technically wrong; unspecified additional assumptions are needed to make it right. Jaynes commented:

"Thus while the QM formalism disagrees with Bell's factorization (14), it appears consistent with what we have called the "fundamentally correct" probability relations [..] . Recognizing this, it is evident that one could produce any number of experimental tests where the predictions of QM conflict with various predictions of (14)."

As that discussion dates far back, it is unlikely that that loophole will ever be closed. Instead, and especially if indeed experimental loopholes are closed to the satisfaction of most, it could be the clue to better insight about "spookiness" which might be not that "spooky" after all.

Unfortunately Jaynes was wrong. He was flaggergasted when Stephen Gull gave an alternative proof of Bell's theorem showing using Fourier analysis that it was impossible to simulate the quantum correlations of the EPR-B experiment on a network of classical computers. http://arxiv.org/abs/1312.6403 http://www.mrao.cam.ac.uk/~steve/maxent2009/ http://www.mrao.cam.ac.uk/~steve/maxent2009/images/bell.pdf
Basically, Jaynes had misunderstood the point of Bell's theorem and thought Bell was making an elementary probability mistake. He wasn't. Jaynes was often right, but not this time.

 

[harrylin]

Unfortunately Jaynes was wrong. He was flaggergasted when Stephen Gull gave an alternative proof of Bell's theorem showing using Fourier analysis that it was impossible to simulate the quantum correlations of the EPR-B experiment on a network of classical computers. http://arxiv.org/abs/1312.6403 http://www.mrao.cam.ac.uk/~steve/maxent2009/ http://www.mrao.cam.ac.uk/~steve/maxent2009/images/bell.pdf
Basically, Jaynes had misunderstood the point of Bell's theorem and thought Bell was making an elementary probability mistake. He wasn't. Jaynes was often right, but not this time.

That's very interesting, thanks!
It will take me some time to absorb it of course...

However, is that a formal proof? Why is it impossible to formally prove it by analytical derivation, as Bell attempted?

 

[gill1109]

That's very interesting, thanks!
However, is that a formal proof? Why is it impossible to formally prove it by analytical derivation, as Bell attempted?

It is a formal proof. There are lots of formal proofs. The mathematical content is essentially trivial. You can prove it by Fourier analysis if you like, by logic and probability theory if you like, by calculus if you like. You can argue about the rigour and the generality of the different proofs. If you use calculus you are assuming calculus rules applies to physics, maybe you're wrong! I prefer an elementary proof by logic and discrete (counting) probability. Such as the proof I developed over the years which also allows to take account of *finite statistics* and *memory* and *time inhomogeneity*. Yet is as (in essence) as simple as they get. http://arxiv.org/abs/quant-ph/0110137 http://arxiv.org/abs/quant-ph/0301059 http://arxiv.org/abs/1207.5103 I'm very proud of the fact that the experimenters are now actually using my techniques to get their "paranoid" p-value (ie allowing any kind of dependence through the past, memory, etc etc ... just using the randomness in the measurement settings. Not assuming any kind of randomness in the physics).

 

[harrylin]

It is a formal proof. There are lots of formal proofs. The mathematical content is essentially trivial. You can prove it by Fourier analysis if you like, by logic and probability theory if you like, by calculus if you like. You can argue about the rigour and the generality of the different proofs. If you use calculus you are assuming calculus rules applies to physics, maybe you're wrong! I prefer an elementary proof by logic and discrete (counting) probability. Such as the proof I developed over the years which also allows to take account of *finite statistics* and *memory* and *time inhomogeneity*. Yet is as (in essence) as simple as they get. http://arxiv.org/abs/quant-ph/0110137 http://arxiv.org/abs/quant-ph/0301059 http://arxiv.org/abs/1207.5103 I'm very proud of the fact that the experimenters are now actually using my techniques to get their "paranoid" p-value (ie allowing any kind of dependence through the past, memory, etc etc ... just using the randomness in the measurement settings. Not assuming any kind of randomness in the physics).

Thanks Richard - that's another thick paper to read!
Concerning the hand-written proof by Gull, I notice the assumption "particle went into + channel (or - channel)"*. And you have "discrete counting probability" ... Could that fall in the category of what Bayes called "Bell theories" or is it really totally general? Can your class of models address the ("non-particulate"!) wave picture of reality as promoted by A. Neumaier (also a member of this forum), based on QFT? It's as yet unclear to me how to fill in your spreadsheet table based on such a picture.

*PS. that contradicts the claim at the bottom of that hand-written pdf that "There are no physical assumptions"!

 

[gill1109]

Thanks Richard - that's another thick paper to read!
Concerning the hand-written proof by Gull, I notice the assumption "particle went into + channel (or - channel)"*. And you have "discrete counting probability" ... Could that fall in the category of what Bayes called "Bell theories" or is it really totally general? Can your class of models address the ("non-particulate"!) wave picture of reality as promoted by A. Neumaier (also a member of this forum), based on QFT? It's as yet unclear to me how to fill in your spreadsheet table based on such a picture.

*PS. that contradicts the claim at the bottom of that hand-written pdf that "There are no physical assumptions"!

Bell (1981): "You might suspect that there is something specially peculiar about spin-1/2 particles. In fact there are many other ways of creating the troublesome correlations. So the following argument makes no reference to spin-1/2 particles, or any other particular particles.

"Finally you might suspect that the very notion of particle, and particle orbit, freely used above in introducing the problem, has somehow led us astray. Indeed did not Einstein think that fields rather than particles are at the bottom of everything? So the following argument will not mention particles, nor indeed fields, nor any other particular picture of what goes on at the microscopic level. Nor will it involve any use of the words ‘quantum mechanical system’, which can have an unfortunate effect on the discussion. The difficulty is not created by any such picture or any such terminology. It is created by the predictions about the correlations in the visible outputs of certain conceivable experimental set-ups.

"Consider the general experimental set-up of Fig. 7. To avoid inessential details it is represented just as a long box of unspecified equipment, with three inputs and three outputs. The outputs, above in the figure, can be three pieces of paper, each with either ‘yes’ or ‘no’ printed on it. The central input is just a ‘go’ signal which sets the experiment off at time t1. Shortly after that the central output says ‘yes’ or ‘no’. We are only interested in the ‘yes’s, which confirm that everything has got off to a good start (e.g., there are no ‘particles’ going in the wrong directions, and so on). At time t1 + T the other outputs appear, each with ‘yes’ or ‘no’ (depending for example on whether or not a signal has appeared on the ‘up’ side of a detecting screen behind a local Stern–Gerlach magnet). The apparatus then rests and recovers internally in preparation for a subsequent repetition of the experiment. But just before time t1 + T, say at time t1 + T – delta, signals a and b are injected at the two ends. (They might for example dictate that Stern–Gerlach magnets be rotated by angles a and b away from some standard position). We can arrange that c delta << L, where c is the velocity of light and L the length of the box; we would not then expect the signal at one end to have any influence on the output at the other, for lack of time, whatever hidden connections there might be between the two ends.

"Sufficiently many repetitions of the experiment will allow tests of hypotheses about the joint conditional probability distribution P(A,B|a, b) of results A and B at the two ends for given signals a and b. Now of course it would be no surprise to find that the two results A and B are correlated, i.e., that P does not split into a product of independent factors: P(A,B|a,b) != P1(A|a)P2(B|b). But we will argue that certain particular correlations, realizable according to quantum mechanics, are locally inexplicable. They cannot be explained, that is to say, without action at a distance."

 

[Demystifier]

While this is the first Bell test that simultaneously addresses both the detection and the locality loophole, am I mistaken that this would still not be considered a loophole-free test?

There is no such thing as "loophole free test". A smart skeptic can always construct a new kind of loophole. If nothing else works, one can invoke a stupidity loophole; maybe nature is still local, but we are just too stupid to explain the correlations with a local theory.

 

[Heinera]

There is no such thing as "loophole free test". A smart skeptic can always construct a new kind of loophole. If nothing else works, one can invoke a stupidity loophole; maybe nature is still local, but we are just too stupid to explain the correlations with a local theory.

No, it suffices that Bell was smart enough to come up with his theorem. It shows that it is impossible to explain the correlations with a local theory, no matter your intelligence.

 

[gill1109]

We know perfectly well what a loophole free test is. It was carefully described by J.S. Bell in 1981. OK so it took 35 years before anyone could do it (and get the expected result).

Of course a sceptic can always come up with ludicrous explanations for the results. Conspiracy. Such explanations have no explanatory power, they make a mockery of physics in general, and Occam's razor deals with them.

One should distinguish between loopholes caused by not doing the good experiment, and loopholes offered by over-the-top metaphysics. Yes, Alice's diamond knows what pseudo random number generator was used to create Bob's settings and that's the explanation for the quantum correlations ...

 

[Demystifier]

No, it suffices that Bell was smart enough to come up with his theorem. It shows that it is impossible to explain the correlations with a local theory, no matter your intelligence.

Bell was very smart, yet there are other smart people who proposed possible alternatives to non-locality:

- Copenhagen - nature is local, but objective reality does not exist (Bohr, Mermin, Rovelli-relational, Zeilinger, ...)

- many worlds - objective reality exists and is "local", but not in the 3-space (Everett, Deutsch, Tegmark, ...)

- superdeterminism - objective reality exists, it is local and deterministic, but initial conditions are fine tuned ('t Hooft)

- backward causation - objective reality exists and is local, but there are signals backwards in time (transactional interpretation)

- noncommutative hidden variables - objective reality exists and is local, but is not represented by commutative numbers (Joy Christian)

- solipsistic hidden variables - objective reality exists and is local, but objective reality describes only the observers, not the observed objects (H. Nikolic, http://xxx.lanl.gov/abs/1112.2034 )

- consistent histories - objective reality exists and is local, but classical propositional logic is replaced with a different logic (Griffiths, http://lanl.arxiv.org/abs/1110.0974, http://lanl.arxiv.org/abs/1105.3932 )

 

[gill1109]

Bell was very smart, yet there are other smart people who proposed possible alternatives to non-locality:

- Copenhagen - nature is local, but objective reality does not exist (Bohr, Mermin, Rovelli-relational, Zeilinger, ...)

- many worlds - objective reality exists and is "local", but not in the 3-space (Everett, Deutsch, Tegmark, ...)

- superdeterminism - objective reality exists, it is local and deterministic, but initial conditions are fine tuned ('t Hooft)

- backward causation - objective reality exists and is local, but there are signals backwards in time (transactional interpretation)

- noncommutative hidden variables - objective reality exists and is local, but is not represented by commutative numbers (Joy Christian)

- solipsistic hidden variables - objective reality exists and is local, but objective reality describes only the observers, not the observed objects (H. Nikolic, http://xxx.lanl.gov/abs/1112.2034 )

- consistent histories - objective reality exists and is local, but classical propositional logic is replaced with a different logic (Griffiths, http://lanl.arxiv.org/abs/1110.0974, http://lanl.arxiv.org/abs/1105.3932 )

Bell was smart. Bell already gave at least five alternatives. However, this experiment removes two of them ("QM is wrong", and "QM prevents us from ever getting experimental proof"). http://arxiv.org/abs/quant-ph/0301059 "Time, finite statistics, and Bell's fifth position" by yours truly.

 

[Heinera]

I obviously implied the impossibility of a local hidden variable theory. The names you list here range from very smart to complete crackpots. Most of these are all metaphysical claims that can be done away with by Occam's razor, and not loopholes in the proper sense.

 

[stevendaryl]

I obviously implied the impossibility of a local hidden variable theory. The names you list here range from very smart to complete crackpots. Most of these are all metaphysical claims that can be done away with by Occam's razor, and not loopholes in the proper sense.

I would only call one of them crackpot. I'm not going to say which, but Richard Gill certainly knows which one.

 

[gill1109]

I would only call one of them crackpot. I'm not going to say which, but Richard Gill certainly knows which one.

OK I am provoked and will give my reactions to the list:

- Copenhagen - nature is local, but objective reality does not exist (Bohr, Mermin, Rovelli-relational, Zeilinger, ...)

I think this is an incorrect view of the Copenhagen interpretation. Measurement outcomes are objectively real. So there is an objective reality. In fact, I buy this one.
- many worlds - objective reality exists and is "local", but not in the 3-space (Everett, Deutsch, Tegmark, ...)

I think this is many words - a smoke screen of words which act as a comfort blanket.
- superdeterminism - objective reality exists, it is local and deterministic, but initial conditions are fine tuned ('t Hooft)

Yes, sure, initial conditions are so fine tuned that the diamond at Alice's place knows all about the pseudo random number generator at Bob's place.
- backward causation - objective reality exists and is local, but there are signals backwards in time (transactional interpretation)

If you want to call that an interpretation...- noncommutative hidden variables - objective reality exists and is local, but is not represented by commutative numbers (Joy Christian)

Pity about the math errors and the new definition of correlation and general lack of any connection to physics in this so-called theory.- solipsistic hidden variables - objective reality exists and is local, but objective reality describes only the observers, not the observed objects (H. Nikolic, http://xxx.lanl.gov/abs/1112.2034 )

Sounds like a word game to me. - consistent histories - objective reality exists and is local, but classical propositional logic is replaced with a different logic (Griffiths,http://lanl.arxiv.org/abs/1110.0974, http://lanl.arxiv.org/abs/1105.3932 )

I have never understood how this succeeds in explaining anything. Basically: let's assume that reality is weird, then QM is no longer weird.
Sorry for being a bit "abrasive". I have thought about all this a great deal the last 20 years and I'm getting old and dogmatic ...

 

[atyy]

- solipsistic hidden variables - objective reality exists and is local, but objective reality describes only the observers, not the observed objects (H. Nikolic, http://xxx.lanl.gov/abs/1112.2034 )

Sounds like a word game to me.

It's more than that. Usually one does some handwaving with the "brain in a vat". But what are the actual equations governing the brain and its stimulation? Here he provides the equations.

- Copenhagen - nature is local, but objective reality does not exist (Bohr, Mermin, Rovelli-relational, Zeilinger, ...)

I think this is an incorrect view of the Copenhagen interpretation. Measurement outcomes are objectively real. So there is an objective reality. In fact, I buy this one.

I don't think this is the standard Copenhagen either. The standard Copenhagen has objective reality, eg. Landau and Lifshitz and Weinberg. I too buy standard Copenhagen.

 

[gill1109]

It's more than that. Usually one does some handwaving with the "brain in a vat". But what are the actual equations governing the brain and its stimulation? Here he provides the equations.

Thanks. I will take a look.

 

[stevendaryl]

Thanks. I will take a look.

Also, just in case you care about insulting people to their face, Nikolic is a regular, and well-respected, participant in this forum (where he uses a pseudonym).

 

[atyy]

- noncommutative hidden variables - objective reality exists and is local, but is not represented by commutative numbers (Joy Christian)

Pity about the math errors and the new definition of correlation and general lack of any connection to physics in this so-called theory.

You were good to give such a serious criticism. But did you read Scott Aaronson's hilarious commentary on your criticism?

"Now, as Gill shows, Joy actually makes an algebra mistake while computing his nonsensical “correlation function.” The answer should be -a.b-a×b, not -a.b. But that’s truthfully beside the point. It’s as if someone announced his revolutionary discovery that P=NP implies N=1, and then critics soberly replied that, no, the equation P=NP can also be solved by P=0." http://www.scottaaronson.com/blog/?p=1028