
There exists a classical model of the photon after all - inglesp
https://www.lightbluetouchpaper.org/2015/02/23/maxwell/
======
Strilanc
Scott Aaronson has commented negatively on a previous paper by the same
authors [1]. I don't know if similar issues apply to this one:

> _[...] the paper advances the prediction that quantum computation will never
> be possible with more than 3 or 4 qubits. [...] I wonder: before uploading
> their paper, did the authors check whether their prediction was, y’know,_
> already falsified _? How do they reconcile their proposal with (for example)
> the 8-qubit entanglement observed by Haffner et al. with trapped ions [...]_

(Note: that's a critique of the previous paper, not the linked one. Although
the linked post mentions quantum computers not working, the linked paper does
not touch the subjet.)

1:
[http://www.scottaaronson.com/blog/?p=1255](http://www.scottaaronson.com/blog/?p=1255)

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btilly
They claim to have found a classical system that reproduces quantum mechanical
effects. But if they manage to extend it to many particles, interacting, they
will find that they have just come up with another interpretation of QM which
is experimentally indistinguishable from the rest. And it wouldn't even be the
first one. (Bohm's hidden variable theory has precedence.)

Furthermore the "incompressible fluid" they postulate sounds like it enables
non-local behavior (which it has to to match current versions of the Bell
test) so it is unable to help resolve the issue of reconciling GM with QM.

So this does rather less than they claim. Assuming that their claimed result
is correct.

~~~
fixermark
What's the current status of Bohm's hidden variable theory? Does it stand up
in light of the Bell test (I was under the impression that the Bell results
suggest an arbitrary number of hidden variables would be necessary)?

~~~
btilly
I don't know and don't keep track. I lost interest after realizing that it can
be made compatible with any possible observation.

I'm personally a fan of the Everett interpretation. Also called the many
worlds. Which is what you get if you assume that quantum mechanics applies to
the observer. Then the act of observation throws the observer into a
superposition of possible states where different things were observed. And
those states cannot meaningfully interact later for thermodynamic reasons.

Unless someone comes up with good reason to believe that quantum mechanics
does not describe humans, I see no reason not to accept it. And if quantum
mechanics is replaced by something different, to the extent that quantum
mechanics is an accurate description of us, that interpretation remains
correct.

~~~
IsTom
There's a problem with with many-worlds that I haven't seen convincingly
refuted: when collapsing superposition of two states you might need to (or
rather almost always) need the ratio of worlds with outcome A to worlds with
outcome B to be irrational. So unless you create a continuum of new worlds
each time it won't work.

~~~
lmm
The wavefunction is a superposition of n independent wavefunctions at
different amplitudes, like you can divide a piano's sound into a bunch of pure
sine waves. "From the inside" each feels like a self-contained world (in a
physically rigorous sense), but the ratio between their amplitudes and phases
can be an arbitrary complex number - just as even if you're only playing a C
and a G, the ratio of their amplitudes can be anything.

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cevn
"Updating this with modern knowledge of quantised magnetic flux, we show that
if you model a flux tube as a phase vortex in an inviscid compressible fluid,
then wavepackets sent down this vortex obey Maxwell’s equations to first
order; that they can have linear or circular polarisation; and that the
correlation measured between the polarisation of two cogenerated wavepackets
is exactly the same as is predicted by quantum mechanics and measured in the
Bell tests."

How long would I have to study physics to be able to understand everything in
this sentence?

~~~
sampo
> How long would I have to study physics to be able to understand everything
> in this sentence?

Just start reading _David J. Griffiths: Introduction to Electrodynamics_. A
very well written textbook. The problem might be, if you don't know vector
calculus, you might not be able to read this book, so you need to learn some
vector calculus, too.

Then start reading _Introduction to Quantum Mechanics_ by Griffiths, too. Best
introductory QM book that I know of. If you managed to read Electrodynamics,
you should by now know enough calculus for this book, too. But you also need
to know about complex numbers here.

The _" inviscid compressible fluid"_ is about fluid mechanics. I don't know
any splendid textbook on that.

~~~
nilkn
I haven't read it, and it may be too advanced for this purpose, but Landau's
books are generally held in extremely high regard and volume six of his Course
of Theoretical Physics is on fluid mechanics.

For what it's worth, volumes two and three cover electrodynamics and quantum
mechanics, respectively.

~~~
sampo
> Landau's books

Landau's presentation is extremely condensed. Griffiths is much more friendly
towards the reader.

I would compare Landau to Knuth's The Art of Computer Programming. Some people
do read them, but the rest of us just hold them in extremely high regard :-).

~~~
jeffwass
The Landau Lifshitz series is absolutely amazing. It works so well with my
brain, entirely concise with just enough textual clarification as needed.

Eg, volume 1 is classical mechanics. By page 3 or so you e already derived the
Lagrangian equations of motion.

------
yiyus
"our paper shows that the main empirical argument against classical models of
reality is unsound.". That's quite an affirmation!

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phkahler
I hope this is as awesome as it sounds. It sums up everything I've been
thinking about quantum physics, from "someone should look closer at Couders
work" to "spooky action at a distance is BS" to "Quantum computers will never
work - see spooky action".

~~~
pbhjpbhj
It's quite exciting to see these sorts of papers.

What fascinates me is that we have achieved so much in the "quantum age" of
the past century using the models derived from a quantum mechanical approach
to physics. That the bedrock [or lack of one] of that could be removed and
provide a better, more consistent, approach seems so counter-intuitive. But
then one recalls how long the Newtonian or Aristotelian approaches [or any
other such system] stood.

Also would this be a return to universal models with an aether: wonder how
Michelson-Morley works with "flux tubes"?

~~~
lmm
The wheel of science turns, but it doesn't turn backward. Einstein refined
Newton, but in no sense represented a return to Aristotle. Perhaps more to the
point, the Bell Inequalities are true and have been experimentally verified;
reality provably contains either nondeterminism or nonlocality. If you find
the model with instantaneous communication along these "flux tubes" easier to
work with then by all means work with it, but it's just another
interpretation; most of us find the nondeterministic but local model is
ultimately easier to reason about.

------
nilkn
When models like this are proposed, a lot of people are interested because of
the philosophical implications of a classical theory of quantum phenomena.

The question I have, though, is this: does this model actually help model
phenomena that we _can 't_ already model? Quantum gravity is the big
spectacular example, but there are many others.

For instance, the Standard Model is very successful at predicting the
anomalous magnetic moment of the electron. But it is not successful at
predicting the same quantity for the muon. There are many other issues with
the Standard Model that aren't so high-flung as quantum gravity.

Are classical models like these, if they can be shown to incorporate multiple
particles interacting simultaneously, capable of going beyond the Standard
Model or merely replicating it?

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vilhelm_s
I don't know any physics, but it seems like a bit of a warning sign that these
new discoveries in fundamental physics are annouced on... a computer security
blog?

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snarfy
> Updating this with modern knowledge of quantised magnetic flux

It sounds like they are using quantum mechanics to explain quantum mechanics.

------
taybin
"if the fundamental particles are just quasiparticles in a superfluid quantum
vacuum"

well obviously.

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tjradcliffe
This paper has a variety of issues, the most glaring of which is that their
"explanation" of the experimental violation of Bell's inequalities
(specifically the CHSH form that has been realized in many experiments on
polarization) is dependent on a _static_ setup of precisely the kind that
Aspect's experiments were intended to avoid.

Aspect's work is one of the most beautiful pieces of careful and precise
experimental testing of an idea in the past half-century, and while it has
been attacked from many perspectives it is still a very robust argument for
the non-locality of reality. One of the important things about it is that the
polarization direction was switched in a quasi-random way after the photons
had left the source. Variations on this trick have been performed since, and
they all agree with the predictions of quantum theory.

The authors say in this paper "The CHSH assumption is not true in Faraday's
model. Instead there is prior communication of orientation along phase
vortices such as(4), communication which the CHSH calculation excludes by its
explicit assumption."

In experiments like Aspects, prior communication is ruled out because the
experimental setup is varied in one arm of the apparatus outside forward light
cone of the other photon. Each photon gets detected before the other one could
possibly know (based on signalling at the speed of light) what polarizer
orientation it should be lined up with.

So this is an interesting bit of work that might be useful in creating
photonic quasi-particles in magnetic fluids that would allow for study of
photon properties that might be difficult to get an experimental handle on
otherwise, but the claim that they have a classical model that violates Bell's
inequalities in a way that is relevant to the actual experimental work done in
this area is considerably overblown.

~~~
GregBuchholz
I'm not a physicist, but I've always wondered about Caroline Thompson's work,
like:

"Chaotic Ball" model, local realism and the Bell test loopholes

[http://arxiv.org/abs/quant-ph/0210150](http://arxiv.org/abs/quant-ph/0210150)

...any thoughts?

~~~
tjradcliffe
The scrutiny that Bell test experiments get from loophole people is always
much appreciated, but the problem with Aspect's results in particular is that
lovely parenthetical remark that appears in several of his figures, to the
tune of "The dotted line is not a fit to the data, but the quantum mechanical
prediction for this result."

While it is easy to imagine selective-detection effects that mess up the
results enough to invalidate the test at the level of the inequality, it is
very, very difficult to maintain all the physics required for precise,
detailed agreement between theory and experiment of the kind that Aspect and
others have shown. Here is an example of a "local realistic model" that
reproduces the quantum mechanical results for in-time coincidences, but
completely messes up any number of auxiliary measurements:
[http://www.tjradcliffe.com/?p=590](http://www.tjradcliffe.com/?p=590)

So while I'd love to see a modern version of Aspect's work using state-of-the-
art entangled photon sources and the like, the likely reason it hasn't been
done is that the odds of it revealing anything new and different are trivially
small (but not zero, of course!)

