Quantum theorem shakes foundations of Quantum Mechanics!

Quantum theorem shakes foundations

After the results of the OPERA experiment cautiously comfirmed FTL neutrinos, another paper with far-reaching implications has surfaced, this time in the field of quantum mechanics.

At the heart of the weirdness for which the field of quantum mechanics is famous is the wavefunction, a powerful but mysterious entity that is used to determine the probabilities that quantum particles will have certain properties. Now, a preprint posted online on 14 November1 reopens the question of what the wavefunction represents — with an answer that could rock quantum theory to its core. Whereas many physicists have generally interpreted the wavefunction as a statistical tool that reflects our ignorance of the particles being measured, the authors of the latest paper argue that, instead, it is physically real.

David Wallace, a philosopher of physics at the University of Oxford, UK, says that the theorem is the most important result in the foundations of quantum mechanics that he has seen in his 15-year professional career. “This strips away obscurity and shows you can’t have an interpretation of a quantum state as probabilistic,” he says.

ArXiv paper here

If I understand it correctly, this result essentially disproves probabilistic interpretations of QM, and those with unreal wavefunction. This includes current mainstream Copenhagen interpretation.

A bit earlier there was also this paper that essentially disproved dualistic theories like Consciousness causes collapse.
In the mainstream, we are now left with Many-worlds interpretation and De Broglie–Bohm theory.

Scientific history in the making? Awesome!

reply to post by Maslo


This is from the Nature article:

But the new paper, by a trio of physicists led by Matthew Pusey at Imperial College London, presents a theorem showing that if a quantum wavefunction were purely a statistical tool, then even quantum states that are unconnected across space and time would be able to communicate with each other.

That doesn't make sense to me.

I skimmed the paper but haven't had time to study it yet.

However the conclusion in the paper itself makes a lot more sense to me from page 4 middle of left column:

If the quantum state is a physical property of a system [ as
it must be if one accepts the assumptions above [ then
the quantum collapse must correspond to a real physical
process. This is especially mysterious when two entangled
systems are at separate locations, and measurement
of one leads to an instantaneous collapse of the quantum
state of the other.

So the wave function collapse is real, and entanglement is mysterious.
The paper supports concluding that the wave function collapse is real. No surprise there.

In some versions of quantum theory, on the other hand,
there is no collapse of the quantum state. In this case, after
a measurement takes place, the joint quantum state of
the system and measuring apparatus will contain a component
corresponding to each possible macroscopic measurement
outcome.

Which version of quantum theory is this?

The paper says this version of quantum mechanics that doesn't think the wave function collapse is real is probably wrong, is that a surprise to anyone?

I found this comment interesting from the Nature link:
www.nature.com...-30652

"Luca D Alessio said:

What is really surprising about the preprint?

If I understood it correctly it can be summarized as:
1) if you know the Wave-Function you know all physical properties
2) if you know ALL physical properties you also know the WF
3) the measurement process (collapse of wave-function) is a real physical process which selects one of the possible outcome

Again, what is surprising about it? "

Frankly I never doubted that the wave function collapse was real.

Also I'm not sure your interpretation of which mainstream theories we are left with is correct, but I'll have to study the paper to confirm that.

It seems that spirituality is kind of way way super high Tech!!

SNC

The multi-verse is the way of looking at things or theory I have adopted there is simply too much supporting evidence.

Originally posted by snc24
It seems that spirituality is kind of way way super high Tech!!

SNC

Yes indeed.

I found this comment to be the best so far of all the comments from the nature link

matteo Staffaroni said: It's usually a good idea to actually read the preprint before taking to the comments section and endorsing the work of someone else . If you're too lazy to read the preprint, I have summarized its essence for you: The authors begin by making two claims, 1) If a quantum state reflects an underlying objective physical reality, then a list of values of physical properties (i.e., commuting observables) should be sufficient to uniquely determine a quantum state. 2) If a quantum state does not reflect an underlying objective physical reality but is merely a mathematical tool for obtaining probabilities concerning the outcome of an experiment, then a list of values of physical properties cannot uniquely determine the quantum state. There may be several distinct states statistically compatible with a given list of values of physical properties. The authors then want to determine whether (1) or (2) is the correct by considering a thought experiment. Suppose you prepare two different quantum states, both of which are compatible with a given list of values of physical properties. Assuming that the outcome of a measurement is determined by the measurement apparatus and the physical properties of the quantum system alone, then the authors CLAIM that you can arrange for a measurement where the apparatus returns results inconsistent with the predictions of quantum mechanics, resulting in a paradox. They then conclude the paradox constitutes proof of the quantum state (or wavefunction) corresponding to and underlying objective physical reality. The problem here is that the results of the thought experiment are, in fact, in accordance with the laws of quantum mechanics. The authors are apparently a bit rusty with the concept of orthogonality in the context of quantum state vectors and basis functions, and consequently they have misinterpreted the outcome of their imagined experiment. Were they to be familiar with such concepts they would have realized that there is no paradox. Just read the paper and actually go over the math. I don't know what more to say. It's embarrassingly obvious...