Quantum theorem shakes foundations

Nature ^ | 17 November 2011 | Eugenie Samuel Reich

[ShadowAce]

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.

“I don't like to sound hyperbolic, but I think the word 'seismic' is likely to apply to this paper,” says Antony Valentini, a theoretical physicist specializing in quantum foundations at Clemson University in South Carolina.

Valentini believes that this result may be the most important general theorem relating to the foundations of quantum mechanics since Bell’s theorem, the 1964 result in which Northern Irish physicist John Stewart Bell proved that if quantum mechanics describes real entities, it has to include mysterious “action at a distance”.

Action at a distance occurs when pairs of quantum particles interact in such a way that they become entangled. 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. As that seems very unlikely to be true, the researchers conclude that the wavefunction must be physically real after all.

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...

[Cvengr]

Yes, but without that thinking, the science is simply measurements and mathematical expressions for given situations.

More important to science is the identification problem,...how to identify reality with those expressions so they may then be subject to rationalism.

The significance of those philosophical arguments is that they changed the perspective of how to identify the math used to explain the phenomenon or even if phenomenon were the real issue to be measured.

[Cvengr]

re: the sinusoidal function etc.

The example of water running down a pane of glass and similar arguments is also studied by Civil Engineers in hydraulics. The sinusoidal function isn’t a significant issue. It is simply a mathematical method available to use when identifying an empirical perception with a a rational perception. Some mathematical constructs are easier than others to identify with our perceptions.

Same could be said for using Reciprocal lattice space when studying Brillouin zones in semiconductor theory.

I concur with the article premise though, that if all the initial mathematical premises were made from physical observations and the identification problem, then even after numerous logical steps in a rigorous analytical argument, each expression should also be capable of being identifiable with a real world situation.

This isn’t always the case with imaginary numbers, but many phenomenon are explicable using imaginary numbers to model their behavior.

Many older physicists using Methods of Theoretical Physics and Applied Mathematics might formulate 100 step proofs in multivariate and tensor mathematics, with only the initial and final and a few intermediate expressions being identifiable with actual phenomenon, but after checking the logic of the rigorous proof, go back through the steps to see where new terms might be grouped together to form other expressions which are several steps away from measurable phenomenon.

[SunkenCiv]

Thanks AdmSmith.

[Paradox]

Awesome link, and I was mostly able to understand the rebuttal. It seems that it is rather obvious, and that the paper talked about in this post will (or should) be laughed off the stage.

[grey_whiskers]

What's the point of constructing a basis out of non-orthogonal vectors anyway?

PS I like Motl's The Reference Frame, I should've thought to read what he had to say on it.

Cheers!

[wideminded]

If two waves are traveling in such a way that they cancel each other out, then how is energy still transferred past the point where they cancel?

Would you have a perfectly flat spot in the ocean -where all waves cancel each other- suddenly a wave appears on the opposit end?

If two water waves of equal amplitude and exactly opposite direction are passing each other, they don't cancel out to make a flat surface. They form a stationary wave that goes up and down but doesn't appear to move sideways. In this wave there are parallel lines on the surface along which there is no up and down motion. So the wave is essentially cancelling out along these nodal lines. How does the wave energy get past these lines? Water sloshes back and forth under the surface.

[Cvengr]

Might be the simplest method to normalize the gauge invariant.