Ranking of Quantum Mechanics interpretations?

[Gerinski]

Is there somewhere something like a ranking of the different interpretations of Quantum Theory, from the most widely embraced by physicists to the least?
Something like physicists voting in a poll ...

 

[Tournesol]

I gather that the decoherence (Zeh) approach is popular, as is Many Worlds.
However, shut-up-and-calculate is ahead by miles.

 

[jackle]

Is decoherence an interpretation? I thought it was a mathematical description of how the wave function collapses or something, although I confess to not knowing.

 

[selfAdjoint]

Is decoherence an interpretation? I thought it was a mathematical description of how the wave function collapses or something, although I confess to not knowing.

There is a mathematical and physical demonstration that the wave function of a system interacting with the big environment "diagonalizes" very quickly - all the mixed states evolve toward pure states. This is decoherence, and as a tendency it is a fact of nature. The attempt to use this fact to avoid quantum weirdness is an interpretation.

 

[Q_Goest]

There's a brief mention of it at Wikipedia http://en.wikipedia.org/wiki/Many_worlds

For example, a poll of 72 leading physicists conducted by the American researcher David Raub in 1995 and published in the French periodical Sciences et Avenir in January 1998 recorded that nearly 60% thought many worlds interpretation was "true". Max Tegmark (see reference to his web page below) also reports the result of a poll taken at a 1997 quantum mechanics workshop. According to Tegmark, "The many worlds interpretation (MWI) scored second, comfortably ahead of the consistent histories and Bohm interpretations." Other such unscientific polls have been taken at other conferences: see for instance Michael Nielsen's blog [1] report on one such poll. Nielsen remarks that it appeared most of the conference attendees "thought the poll was a waste of time".

The Max Tegmark results are given here:
http://arxiv.org/PS_cache/quant-ph/pdf/9709/9709032.pdf

Interpretation / Votes
Copenhagen / 13
Many Worlds / 8
Bohm / 4
Consistent histories / 4
Modified Dynamics / 1
None of the above/undecided / 18

 

[graffix]

For all intent and purposes, is the MWI our best GUESS at what's going on, since from what I understand Copenhagen is the "stick to the math", "don't worry about philosohpy" interpretation (if it is an interpretation)?

 

[moving finger]

I gather that the decoherence (Zeh) approach is popular, as is Many Worlds.
However, shut-up-and-calculate is ahead by miles.

except that shut-up-and-calculate is not an interpretation, it is instead a refusal to interpret.

Thank goodness that scientific truth is not decided by democratic elections!

MF

 

[Tournesol]

The Copenhage "interpretation" also refuses to say anything about the
reality or nature of unobserved SVs/WFs.

 

[moving finger]

can someone summarise just what needs to be interpreted?

MF

 

[selfAdjoint]

can someone summarise just what needs to be interpreted?

MF

In the quantum mechanics math, which works so well and makes such accurate predictions, the "reality" of, say, an electron is represented as a vector in an infinite dimensional abstract space, or you could think of it as a wave, but whichever way you look at it, it's not a feature of our world. When we make observations, that's represented in the math as and operator - like an infinite dimensional matrix - acting on the vector, or the wave, and it produces a set of real numbers. These numbers are interpreted as the probability of seeing the electron at various points, or with various different momenta.

So this mathematics doesn't tell us anything about the behavior of the electron in this world, it is just about our observations and the probabilities of what we will see. The interpretations of quantum mechanics are intended to provide some idea of what the math means.

 

[moving finger]

In the quantum mechanics math, which works so well and makes such accurate predictions, the "reality" of, say, an electron is represented as a vector in an infinite dimensional abstract space, or you could think of it as a wave, but whichever way you look at it, it's not a feature of our world.

In other words, our concepts of "wave" and "particle" do not apply to quantum objects. There is no simple analogy from the macroscopic world which helps us to visualise a quantum object.

When we make observations, that's represented in the math as and operator - like an infinite dimensional matrix - acting on the vector, or the wave, and it produces a set of real numbers. These numbers are interpreted as the probability of seeing the electron at various points, or with various different momenta.

So this mathematics doesn't tell us anything about the behavior of the electron in this world, it is just about our observations and the probabilities of what we will see. The interpretations of quantum mechanics are intended to provide some idea of what the math means.

Thank you. It seems to me then, on this basis, that neither "shut up and calculate" nor the Copenhagen "interpretation" are true interpretations (neither gve us any idea of what the math means)? An interpretation should purport to give us some insight into ontology, into what is really going on - neither "shut up and calculate" nor "Copenhagen" claims to do this.

MW is an interpretation. Decoherence is an interpretation. Bohmian mechanics is an interpretation. Feynman-Wheeler/Transactional theories are also interpretations.

MF

 

[jackle]

...It seems to me then, on this basis, that neither "shut up and calculate" nor the Copenhagen "interpretation" are true interpretations (neither gve us any idea of what the math means)? An interpretation should purport to give us some insight into ontology, into what is really going on - neither "shut up and calculate" nor "Copenhagen" claims to do this...MF

In my personal studies, the greatest revelations of all have come from considering these interpretations. eg. That the universe may be capable of pure randomness or operate in ways that will remain impenetrable to experiment forever. I find these very satisfying insights into ontology. I'd sooner concede this, than believe in unthinkable numbers of different universes I can never get to, or accept that we are surrounded by advanced waves traveling the wrong way through time (although I like to flirt with these ideas to, from time to time ).

 

[moving finger]

In my personal studies, the greatest revelations of all have come from considering these interpretations. eg. That the universe may ... operate in ways that will remain impenetrable to experiment forever.

How can one achieve a "revelation" from something that remains "impenetrable to experiment forever"? Grateful for your insights here.

If the universe is "impenetrable to experiment forever", there is not much point in discussing it further, is there?

I'd sooner concede this than ... accept that we are surrounded by advanced waves traveling the wrong way through time

Can you explain results of entanglement experiments, or the results of the delayed choice experiment, in any other way?

Cheers

MF

 

[jackle]

How can one achieve a "revelation" from something that remains "impenetrable to experiment forever"?

The impenetrability is a revelation to me.

Can you explain results of entanglement experiments, or the results of the delayed choice experiment, in any other way?

No, it would involve maths that are long since beyond me anyway.

 

[Q_Goest]

can someone summarise just what needs to be interpreted?
MF

Zeilinger did a pretty decent job of this in a paper he published in 1999:
http://www.quantum.univie.ac.at/zeilinger/foundations.pdf

Physics in the 20'th century is signified by the invention of the theories of special and general relativity and quantum theory. Of these, both the special and general theory of relativity are based on firm foundational principals, while quantum mechanics lacks such a principal to this day. By such a principal, I do not mean an axiomatic formalization of the mathematical foundations of quantum mechanics, but a foundational conceptual principal. In the case of the special theory, it is the Principal of Relativity, stating that all laws of physics must be the same in all inertial reference frames, independent of their state of relative motion. In the case of the theory of general relativity, we have the Principal of Equivalences: "In a gravitational field (of small spatial extension), things behave as they do in a space free of gravitation, if one introduces, in place of an "inertial system," a reference system that is accelerated relative to an inertial system." Both foundational principals are very simple and intuitively clear.

The above describes "foundational principals" which provide a conceptual framework for relativity. He points these out as an example of 'foundational principals'. Another example of a foundational principal would be for the first law of thermodynamics which is the conservation of energy. The foundational principal for the first law states that energy is conserved and thus we can use this basic concept to formulate a mathematical approach to the first law.
He then goes on to say such foundational principals don't exist for QM.

In quantum mechanics, to the contrary, we do observe the presence of a broad discussion about the interpretation of the theory. In fact, we have a number of coexisting interpretations utilizing mutually contradictory concepts. … I suggest that the message is that a generally accepted foundational principal for quantum mechanics has not yet been identified.

He then explains two different levels of interpretation of a theory, 1) how to verify theoretical predictions using essentially mathematical formulas and 2) "on the meta-level, less operational (mathematical) but conceptually more significant, interpretation means an analysis of what the theory implies for our general view of the world … "
He suggests that on the first level, all interpretations are essentially identical, they lead to the same experimental predictions. But on the second level of interpretation, there seems to be no agreement. The Copenhagen Interpretation is obviously very different from the Many-Worlds Interpretation.
So what needs to be interpreted is this second level where there are no foundational principals for quantum mechanics.
There is also an interesting article here regarding Zeilinger's work into the foundational principals of quantum mechanics:
http://www.quantum.univie.ac.at/links/newscientist/bit.html

 

[moving finger]

How can one achieve a "revelation" from something that remains "impenetrable to experiment forever"?

The impenetrability is a revelation to me.

I see. And the fairies at the bottom of my garden are a revelation to me. But pointless nevertheless.

I'd sooner concede this than ... accept that we are surrounded by advanced waves traveling the wrong way through time

Can you explain results of entanglement experiments, or the results of the delayed choice experiment, in any other way?

No, it would involve maths that are long since beyond me anyway.

With respect, if you have no way of explaining a particular phenomenon of the physical world (such as the results of delayed choice experiments) then you have no rational basis for rejecting a possible explanation (the transactional interpretation of QM).
MF

 

[moving finger]

He then goes on to say such foundational principals don't exist for QM.

OK, I follow this (I think). And I tend to agree (with reservations). There is (to my mind) a "partial" foundational principle (or one could say there is the beginnings of a foundational principle) for QM, and that is the fact that all mass/energy is quantised (the fundamental principle which allowed Planck to explain blackbody radiation and lay the basis for quantum theory in 1900). The problem is that this principle (the fact that all mass/energy is quantised) is apparently not sufficient to generate all of the weirdness of QM. We need something more. In the early decades of the 20th century Bohr added the principle of complementarity; Heisenberg added the principle of uncertainty; Pauli added the exclusion principle, and all of these principles are intertwined in QM. More recently Bell/Aspect and others have added the principle of entanglement. But still all of this is insufficient to arrive at a complete foundational principle for QM.

He then explains two different levels of interpretation of a theory, 1) how to verify theoretical predictions using essentially mathematical formulas

imho, "verifying theoretical predictions using mathematical formulas" (the "shut up and calculate" approach) does not constitute an "interpretation".

and 2) "on the meta-level, less operational (mathematical) but conceptually more significant, interpretation means an analysis of what the theory implies for our general view of the world … "

imho this is closer to what most people mean when they talk of an "interpretation".
Let me use the analogy of learning a hypothetical foreign language, such as Klingon. One could learn how to spell all of the words in Klingon (but WITHOUT knowing what these words mean in English), learn all of the grammatical principles and rules and syntax that allow us to combine these non-understood words together to form legitimate Klingon sentences, and on this basis one could then construct valid and legitimate sentences in Klingon, WITHOUT KNOWING WHAT THE SENTENCES MEAN IN ENGLISH.
The "interpretation" provided by Copenhagen, and even worse the "shut up and calculate" approach, is imho the equivalent of learning how to construct valid Klingon sentences without knowing what these sentences mean in English.
What we need imho is an interpretation of QM which is equivalent to constructing sentences in Klingon and at the same time being able to translate those sentences into a language that we do understand (which Copenhagen does not do). What does this mean in practice? It means being able to find models and/or analogies which allow us to translate the maths of QM into meaningful ideas/pictures/representations that we can relate to, that provide us with the meaning and understanding of the underlying ontology. It has been the apparent impossibility of doing this over the last 100 years of QM that has prevented us from arriving at such an interpretation.
MF

 

[moving finger]

MW is an interpretation. Decoherence is an interpretation. Bohmian mechanics is an interpretation. Feynman-Wheeler/Transactional theories are also interpretations.
MF

Having thought about this a bit more, I now delete Decoherence from my list of possible interpretations. Decoherence explains the phenomenon known colloquially as "collapse of the wavefunction", but it does not provide a complete interpretation of QM, therefore imho does not qualify on its own as an interpretation (although it could form the basis for an interpretation).

MF

 

[jackle]

The impenetrability is a revelation to me.

I see. And the fairies at the bottom of my garden are a revelation to me. But pointless nevertheless.

I think this is a little bit unfair. I'm not insisting that aspects of the universe can be impenetrable to experiment indefinately, but shut-up-and-calculate would be plain wrong if we can expose the underlying mechanism behind quantum mechanics. Doesn't shut-up-and-calculate raise the issue of penetrability and isn't this a valid and interesting question?

...you have no rational basis for rejecting a possible explanation (the transactional interpretation of QM).

No I don't. The transactional interpretation is quite valid, and I like I say, I have flirted with it a bit in the past.

 

[moving finger]

I think this is a little bit unfair.

Yes, I apologise for that. I was being far too flippant.
But with respect, it seems to me that impenetrability at the quantum level is logically inevitable and should not really be a surprise to anyone. Even with no knowledge of QM, Planck's constant and Heisenberg's uncertainty principle, it is logically quite clear that the classical experimental paradigm (viz the "observer" can always be totally isolated from the "observed") must break down at some point as we go to finer and finer observations.

I'm not insisting that aspects of the universe can be impenetrable to experiment indefinately,

however I do in fact believe that aspects of the universe will be impenetrable to experiment for ever - for the reasons above.

but shut-up-and-calculate would be plain wrong if we can expose the underlying mechanism behind quantum mechanics. Doesn't shut-up-and-calculate raise the issue of penetrability and isn't this a valid and interesting question?

imho shut-up-and-calculate (suac) is perfectly fine for the purpose intended, which is for making quantitative predictions of quantum behaviour where such predictions are possible. However, to my mind "suac" does not constitute an interpretation of QM. Because it is not an interpretation, 'suac' avoids the issue of penetrability.
MF

 

[moving finger]

some more reflections...
The Copenhagen Interpretation (CI) recognises that there is an epistemic horizon beyond which we cannot "know" anything. In strict scientific tradition, therefore, the Copenhagenist must draw a line at this point and say "this far and no further" - which is exactly what Bohr does. To speculate as to what may or may not lay beyond, since it is beyond the reach of experiment, is metaphysical and non-scientific, and hence scientifically non-sensical. In this sense, CI takes the interpretation "as far as it can" within the rules of scientific exploration, and acknowledges that any further "interpretation" is in fact pure speculation.
But some of us are unhappy about this state of affairs. For some of us it seems intuitively obvious that there must be "something" beyond that epistemic horizon, and if current science is unable to identify what that something is then so much the worse for current science.
The ideas behind MW, hidden variables, Transactional Interpretation, are all speculative. But I see nothing wrong with speculation, once you have reached the end of the scientific method...
MF

 

[jackle]

One day we may have a breakthrough and find a way to test which interpretation is correct. Hopefully there is a lot of human history still to unfold.

 

[moving finger]

One day we may have a breakthrough and find a way to test which interpretation is correct. Hopefully there is a lot of human history still to unfold.

I hope so too, even though my scientific training tells me it's a "no brainer".
But they say that hope springs eternal in the human breast... maybe that's why humans will always be better than machines (or Vulcans).

MF