
Interpretations of quantum theory: A map of madness - mathgenius
http://arxiv.org/abs/1509.04711
======
pygy_
This paper gives the context in which this other one has been written:
[http://arxiv.org/abs/1509.03641](http://arxiv.org/abs/1509.03641)

Discussed 13 hours ago:
[https://news.ycombinator.com/item?id=10228435](https://news.ycombinator.com/item?id=10228435)

------
themgt
Mermin put it perhaps most succinctly, that reality is "correlations without
correlata", or as Ron Garret coined, the "zero-worlds interpretation"[1]

It also makes sense to me on a sociological level, that the way in which this
interpretation seems to undermine the very foundation of western, scientific
thought is the reason it has been so desperately avoided for so long, with
many preferring to believe in an infinite forking (but somehow still "real)
multiverse, than the idea that reality itself is intersubjective.

[1]
[https://www.youtube.com/watch?v=dEaecUuEqfc](https://www.youtube.com/watch?v=dEaecUuEqfc)

~~~
westoncb
Regarding "correlations without correlata": this feels to me like we are
starting to hit on properties on our mechanism for describing/representing and
confusing it with what we're trying to describe/represent. Rather than saying
there's "nothing really there," couldn't it just be a property of human
conceptual structure that it expresses abstract relations about abstract
symbols, but there are never any 'things' that are related?

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madaxe_again
"We must consolidate into single school of thought"?

Scientific method, much. This is the thinking that lead to pilot wave qm being
disregarded for a few generations.

If anything, pilot wave gives the easiest explanation of locality - there is
none, and it's a deterministic universe.

~~~
darkmighty
That's not exactly the point of this paper (and the quote above is not in it?)

> these two types [of interpretations] are so radically different that there
> _must_ be experiments that, when analyzed outside the framework of quantum
> theory, lead to different empirically testable predictions

------
ThePhysicist
The main problem with interpretations of quantum phenomena is that even today
many physicists receive very little information about modern concepts in
quantum mechanics (QM) during their University training. The standard QM
course usually starts off by explaining the two "postulates" of quantum
mechanics, i.e. that a state is described by a wave function which evolves in
a totally predictable fashion, but which suddenly "collapses" to a classical
state in a random and non-predictable way when we perform a measurement on the
quantum system.

Unfortunately, this picture is almost completely wrong. In fact, there is no
randomness and non-predictability in quantum mechanics. The fact that we
observe wave function collapse in a quantum system is the consequence of
coupling the system to a larger, external one that becomes entangled with the
"small" quantum system and -through so-called decoherence- produces what we
call the collapse of the wave function to a "classical" state. This process is
entirely deterministic.

The theory of such "open quantum systems" is well established today and
explains many of the seeming paradoxes that have plagued quantum mechanics,
and it also provides clear answers to many of the questions posed in the
article.

Some questions, in particular what happens to the parts of the wave function
that do not become part of our reality after a collapse cannot be answered by
any known theoretical framework, hence different people will have different
opinions concerning those. The problem here is that we ourselves are described
by a quantum wave function and therefore "live" inside the quantum world, we
can therefore not "step back" and look at a wave function from the outside,
which is why we can't answer what happens with the parts of a wave function
that correspond to measurement results that we have not obtained when
measuring an observable of a quantum system. Different interpretations of
quantum mechanics like the "Many Worlds" or the "Copenhague" varieties are
basically just arguing about what happens with a wave function after it
"collapses".

To my knowledge there is no way to discriminate between different alternatives
here, the preferences that individual physicists have in this matter are
therefore based more on personal belief or concepts like simplicity or
"beauty", hence we should not waste time trying to find out which is the right
one.

~~~
evanb
The Many Worlds interpretation is the idea that the wavefunction never, ever
collapses. It just evolves unitarily according to the Schrodinger equation
forever.

~~~
effie
Absence of collapse is not endemic to many worlds interpretation. Statistical
interpretation does not talk about collapse either. A better characterization
of many worlds is that the Schroedinger equation is put above anything else,
even above the experiment and existence of definite measurement results.

------
nabla9
Locality in in quantum theory confuses the proverbial journalist because
meaning of locality is different from the intuitive understanding of the word.

Two entangled particles light years apart share state. Physicists can still
say that principle of locality is not violated because definition of locality
in physics is does not include quantum state.

Quantum states have no location. Quantum correlations are non-local. As long
as this is excluded from definition of locality everything is fine.

Information transfer and energy transfer follows principle of locality
strictly.

~~~
darkmighty
I don't think that's correct? Bell's theorem implies you can't have a theory
of local hidden variables that reproduces entanglement (and the rest of QM),
no?

~~~
nabla9
Quantum state is not local hidden variable. It's non-local.

------
ThomPete
The issues with explaining QM today seems to be that the math and experimental
parts are all as tested and proven as they possible can be just as much as
classical physics. Whats putting sand in the machine is that it just doesn't
make sense philosophically.

So if you will allow a complete novice some wild speculation here to provide a
different perspective.

Maybe they are just two different fields with a different base premise and
maybe thats ok.

Perhaps what is really shown here, is the limits of western thought process.

I have always wondered if zen buddhisms way to deal with reality, is much
better capable at explaining whats going on because it's comfortable dealing
with paradoxes ("If it's not paradoxical it's not true" as Zen Master Suzuki
Roshi wrote).

I am not a zen buddhist and there is a big risk that I as a westerner don't
understand zen buddhism (I know i don't understand QM) but it seems to me that
western semantics and rhetorics are actually getting in the way of providing
us with a way to be at ease with what seems to be a fact; that we can't
explain QM through language.

~~~
marcosdumay
It looks like the "shut-up and calculate" school is the one with most adepts.
It's also very zen-like to me (or I completely don't understand what zen is,
not an unlikely alternative).

The problem is that the imaginary journalist has an agenda and will completely
ignore any "shut-up and calculate" answer. The author really needs to make a
better case about the interpretations having different empirical outcomes,
because it's not obvious at all.

~~~
ThomPete
I don't think you are wrong at all in fact I think you are very much correct
in the sense that the answer can't be formulated in language other than one
closer to what it is and there mathematics is closer than english.

Problem is that mathematics isn't enough to make it useful (i.e. predictable)
you need a combination of math and experiments to turn it into something that
can be used.

~~~
marcosdumay
Hum, the "shut-up and calculate" idea is that the theory works, people've
tested it. Now you either use it, or go find empirical flaws, so people can
improve the theory. But thinking about the reasons your math looks like that
has no use, unless you get something with observable consequences, don't waste
the time.

There's nothing in it about math being a perfect language, or experiments not
being necessary.

~~~
ThomPete
Yes thats we have scientist and mathematicians for. That doesn't mean we
shouldn't try and also see if we can put it in different perspectives that
help us understand the field.

If you want to shut-up and calculate by all means. That doesn't mean I or
others have to. After all we are humans.

~~~
marcosdumay
No, I don't want you to follow it. In fact, my personal ideas are a bit
different too.

But it is the most usual approach (or, at least, almost everybody works under
it almost all the time - but people may identify with somehting else), and the
article didn't make a good claim for why we shouldn't just shut-up and
calculate.

~~~
ThomPete
Thats a completely fair point, however I wasn't basing it on this alone :)

------
stared
Still (and I am a quantum physics PhD) I don't get what is wrong with having
many _interpretations_. Especially, as in physics there are many other
phenomena that can be _interpreted_ in different ways. For the simplest:
movement as forces vs as a teleological least action principle.

While for some phenomena one is easier that the other, considering that there
should be only one "true" interpretation, is, at best, narrow-mindness (and at
worst: dogmatism, a very enemy of science).

~~~
iofj
Well the reason that it is "wrong" is that for many people (generally the ones
outside of scientific endeavours) the interpretations are physics. Let's face
facts : most people are never going to learn even basic physics beyond high
school level, and oversimplified "philsophy" is all they'll ever know. (As my
philosophy professor said: history seems to indicate that science is the way
to be right, and philosophy is the science of being wrong)

And the opinion that interpretation doesn't matter, there's equations, and
what they say takes precedence over whatever a human mind produces. That they
don't fit well in any of these "interpretations" merely amplifies that belief
(as it should).

It's a matter of perspective.

~~~
stared
Some interpretation may matter, as e.g. they can be more fruitful in
generating new predictions, or extending a theory. And some may turn out to be
wrong (e.g. the hidden variable interpretation, which before Bell was
considered just a different interpretation).

So my impression is that the lay audience like hearing big words, even if they
cannot understand it at all (but it is easier to delude oneself that one
understands "many words" than a particular set of equations).

------
buffoon
Well that was more abstract and citations than body. Slightly disappointed.

~~~
mathgenius
I was too but then, well that's the point maybe: There's not much to be said
about all of these interpretations.

------
zamalek
> As Mermin points out, “quantum theory is the most useful and powerful theory
> physicists have ever devised. Yet today, nearly 90 years after its
> formulation, disagreement about the meaning of the theory is stronger than
> ever. New interpretations appear every day. None ever disappear”

Isn't this the essence of science (excluding the last sentence)? The
widespread conflicting interpretations of QT is something to be proud of,
every time a new interpretation is dreamed up it's yet another opportunity to
draw closer to the truth. Science is a field where being wrong should be seen
as a good thing and that certainly _used_ to be the case.

~~~
azernik
The problem is that _nothing is being proven wrong_. Science doesn't advance
by the proliferation of theories, but by their narrowing into a smaller set of
theories that agree on more and more points.

~~~
effie
Well said. All the various opinions aren't going to matter much if
"professionally unsafe" decisive experiments will not be suggested or if those
suggested are not performed.

------
misnome
> At the end of the day, the journalist asks: "How do you plan to make
> progress if, after 90 years of quantum theory, you still don't know what it
> means?

Maybe not asking for lay-person descriptions would gain more consistency.
Also, it says "A Group of Physicists" which is remarkably vague - physics is a
vast field, and picking random scientists doesn't guarantee actually finding
someone who has more than a basic grasp (not a criticism of the individual
scientists).

~~~
mathgenius
I think this is a well observed phenomenon [1],[2]. At least in the
theoretical quantum group I am in: there is very little agreement about the
interpretation of quantum theory. (Maybe the experimentalists don't care as
much.)

[1] [http://www.preposterousuniverse.com/blog/2013/01/17/the-
most...](http://www.preposterousuniverse.com/blog/2013/01/17/the-most-
embarrassing-graph-in-modern-physics/)

[2] [http://arxiv.org/abs/1301.1069](http://arxiv.org/abs/1301.1069)

------
dghf
"Shut up and calculate."

\-- Richard Feynman (attrib.)

