Study claims classical physics is also "weird"

#1
http://phys.org/news/2015-02-classical-theory-weird-quantum.html

Quantum mechanics is often described as "weird" and "strange" because it abandons many of the intuitive traits of classical physics. For example, the ideas that the world is objective, is deterministic, and exists independent of measurement are basic features of classical theory, but do not always hold up in quantum theory. But what if it turns out that these intuitive ideas are not true features of classical physics, either? Would classical theory be just as weird as quantum theory?


In a new study published in Physical Review Letters, physicists Radu Ionicioiu, et al., have shown that the three apparently reasonable classical assumptions mentioned above—objectivity, determinism, and independence—are mutually incompatible with any theory, not only with quantum mechanics. The scientists show that, while any two of the three assumptions are compatible, all three are not. All told, our seemingly reasonable classical assumptions may not be so reasonable after all.

"Sometimes classical ideas may seem 'natural' and 'logical' simply because we do not test them too strongly," coauthor Daniel Terno at Macquarie University in Sydney, Australia, told Phys.org. "Quantum mechanics may be weird, but our classical illusions may be weird too—or simply impossible to maintain, no matter how the world really operates."

The findings could have widespread implications. For many decades, physicists have assumed that our everyday classical ideas are consistent with each other, and have used them to investigate the tensions between the classical and quantum world views. Hidden variable theories, for example, attempt to complete or improve quantum mechanics by reproducing the results of quantum theory while incorporating these classical intuitions. If the new findings are correct, then they will demand that physicists question the basic tenets not only of quantum theory, but of classical theory, as well.

"Our take from this project [a warning: not a theorem, but an opinion] is that because the classical intuitions may be as weird as the quantum predictions, the entire motivation of the hidden variable program to explain quantum mechanics is somewhat pointless," Terno said. "There is no reason to exchange one type of weirdness for another, or to accept some and try to explain away the rest."

The uncovered incompatibility of the three assumptions centers on the quantum phenomenon of wave-particle duality. In their study, the physicists analyzed a version of the delayed-choice experiment, which demonstrates wave-particle duality with an interferometer. In this experiment, a photon behaves as a particle when the interferometer is open and as a wave when it is closed.

The experiment shows that, at any moment in time, a photon cannot be considered as either just a particle or just a wave, depending on the experimental set-up, but instead it has both properties. The experiment builds on the authors' previous work, in which they show how to simplify the demonstration of wave-particle duality.

In the new work, the researchers questioned the usual assumption that classical ideas, even if incompatible with quantum mechanics, are consistent. Here, objectivity is defined as a photon being either a particle or a wave, but not both. Determinism means that the outcome (whether the photon is a particle or a wave) can be determined if all information about the scenario, including any hidden variables, is known. Independence means that the outcome does not depend on the specific experimental setting.

As the physicists explain, because the photon demonstrates both particle and wave behavior in the two different experimental setups, then trying to satisfy all three requirements makes it impossible to have any experimental result at all. As long as different experimental setups yield different types of behavior, then the three intuitive ideas are incompatible, no matter what kind of theory is used. Terno explains this idea using an analogy with an overly demanding client:

"Our result was built similarly to what an annoying client wants from a travel agent: 'I should have this and that, and here and there, but not such and such, and definitely not this way...,' and at the end, no itinerary can satisfy all of the client's constraints. Something has to give.

"When one imagines a hidden variable theory that describes the experiments we consider, it has only so much freedom (seven parameters, to be exact). Putting constraints that are mathematical expressions of our three intuitive requirements reduces the freedom until nothing is left."

Because any two of the three ideas are mutually compatible, the physicists suggest that it seems most natural to drop the objectivity assumption, while keeping determinism and independence. This choice requires that wave-particle duality be accepted, regardless of its counterintuitive nature. However, knowing for sure will be a subject of future research.
 
#3
The experiment shows that, at any moment in time, a photon cannot be considered as either just a particle or just a wave, depending on the experimental set-up, but instead it has both properties. The experiment builds on the authors' previous work, in which they show how to simplify the demonstration of wave-particle duality.
I find this hard to believe given what I have read of quantum physics. It seems more like an attempt to redefine what is meant by particle or wave. It has been demonstrated via the two slit experiment that photons will act either as waves or particles but not both depending on when they are observed. The wave itself is not material in the way any of us think of something actually being present. It is simply a word used by quantum physicists to describe something that literally does not exist physically as an actual fact or object. The quantum wave function is where quantum theory tells us photon particles come from but the wave itself does not exist locally - it is a non-local phenomena.

I'm probably missing something here, but as far as I know, there has never been a demonstration in QM showing both properties being present at once. It is one or the other.

My Best,
Bertha
 
#4
I'm probably missing something here.
Yes you are. Read through the article again. And bear in mind that it's not a QM experiment.

Anyway, even in QM what they state is correct. There's a reason the phenomenon is wave-particle duality. You are thinking of "quantum collapse" through observation.
 
#5
Saiko,

I don't understand, they seem to be arguing that classical physics is weird by using the archetypal QM experiment.

Even so, it seems to me that classical physics is obviously 'weird' in that it couldn't ever explain chemistry. A classical atom would suffer from a number of impossible 'features'. In particular, you could just add some extra energy to the 'orbit' of an electron and change the properties of the atom in a gradual way - just as you could add energy to a planet and move it into a higher orbit. In other words, chemistry would deal with stuff whose properties would just vary from sample to sample - and indeed from atom to atom!

In other words, in retrospect, classical physicists should have already known their ideas were incomplete, long before QM was known about.

Of course, I think they are still incomplete because they don't include consciousness.

David
 
C

Chris

#6
I don't understand, they seem to be arguing that classical physics is weird by using the archetypal QM experiment.
I think when the article talks about classical theories, it's essentially directed at hidden variable theory, which tries to fix up quantum mechanics so things can be deterministic.
 
#7
Saiko,

I don't understand, they seem to be arguing that classical physics is weird by using the archetypal QM experiment.
Not quite. They repurposed one of the archetypal QM experiment in a classical format.

Here instead we study the mutual compatibility of apparently reasonable classical assumptions. We analyze a version of the delayed-choice experiment which ostensibly combines determinism, independence of hidden variables on the conducted experiments, and wave-particle objectivity (the assertion that quantum systems are, at any moment, either particles or waves, but not both). These three ideas are incompatible with any theory, not only with quantum mechanics.
http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.114.060405
 
#8
Small synchronicity I just found this article:
https://www.lightbluetouchpaper.org/2015/02/23/maxwell/

Which sounds interesting although I am not able to fully grasp all the ramifications.

If our sums add up, the consequences could be profound. First, it will explain why quantum computers don’t work, and blow away the security ‘proofs’ for entanglement-based quantum cryptosystems (we already wrote about that here and here). Second, if the fundamental particles are just quasiparticles in a superfluid quantum vacuum, there is real hope that we can eventually work out where all the mysterious constants in the Standard Model come from. And third, there is no longer any reason to believe in multiple universes, or effects that propagate faster than light or backward in time – indeed the whole ‘spooky action at a distance’ to which Einstein took such exception. He believed that action in physics was local and causal, as most people do; our paper shows that the main empirical argument against classical models of reality is unsound.
 
#9
Small synchronicity I just found this article:our paper shows that the main empirical argument against classical models of reality is unsound.
lol. People have been coming up with such claims since the emergence of QM. So far none of them have stuck. I'd guess it's because whatever model may be more accurate than QM will not be found in the classical models. One thing I notice in those claims is that they always have a "religious" agenda. IOW they are obviously motivated because something in QM challenges strong beliefs.

Also, the results presented in the topic of this thread if correct render their conclusions even more adrift.
 
#10
Well, the whole universe seems to be quantum "mechanical " ,including the macro part of it that seems to be "governed " by classical physics ,so QM has to be underlying classical physics even at the macro-level thus lol

Classical physics is not weird thus , just its underlying QM ...The latter is the deeper level of the former .

No wonder that quantum effects are being discovered at more and more macro levels ...

Technology will be so sophisticated some day as to show that quantum effects do happen even at our daily human -scale level lol
 
#11
I think when the article talks about classical theories, it's essentially directed at hidden variable theory, which tries to fix up quantum mechanics so things can be deterministic.
Indeed : those bloody materialist reductionists are trying to reshape QM to their own classical deterministic mechanical materialistic image lol , to try to avoid the fact that since classical physics upon which materialism was built is approximately correct and fundamentally false , then materialism is also false together with its classical determinism ,and has been superseded by QM .
 
#12
If you can't beat QM , then try to make classical deterministic physics/classical deterministic materialism look like it lol

The above article is yet another unintended evidence that supports the observer effect in physics , in the rest of science and in life in general lol
 
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