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from the quantum-reality-is-just-classical-reality-in-really-tiny-bits? dept.
For nearly a century, "reality" has been a murky concept. The laws of quantum physics seem to suggest that particles spend much of their time in a ghostly state, lacking even basic properties such as a definite location and instead existing everywhere and nowhere at once. Only when a particle is measured does it suddenly materialize, appearing to pick its position as if by a roll of the dice. This idea that nature is inherently probabilistic -- that particles have no hard properties, only likelihoods, until they are observed -- is directly implied by the standard equations of quantum mechanics. But now a set of surprising experiments with fluids has revived old skepticism about that world-view. The bizarre results are fueling interest in an almost forgotten version of quantum mechanics, one that never gave up the idea of a single, concrete reality.
In a groundbreaking experiment, the Paris researchers used the droplet setup to demonstrate single- and double-slit interference. They discovered that when a droplet bounces toward a pair of openings in a damlike barrier, it passes through only one slit or the other, while the pilot wave passes through both. Repeated trials show that the overlapping wavefronts of the pilot wave steer the droplets to certain places and never to locations in between — an apparent replication of the interference pattern in the quantum double-slit experiment that Feynman described as "impossible ... to explain in any classical way." And just as measuring the trajectories of particles seems to "collapse" their simultaneous realities, disturbing the pilot wave in the bouncing-droplet experiment destroys the interference pattern.
Droplets can also seem to "tunnel" through barriers, orbit each other in stable "bound states," and exhibit properties analogous to quantum spin and electromagnetic attraction. When confined to circular areas called corrals, they form concentric rings analogous to the standing waves generated by electrons in quantum corrals. They even annihilate with subsurface bubbles, an effect reminiscent of the mutual destruction of matter and antimatter particles.
How about it Soylentils. Is there anyone here who groks Quantum Mechanics who would care to explain this in layman's terms? What shortcomings and/or benefits do you see with this theory?
(Score: 4, Interesting) by boristhespider on Tuesday July 01 2014, @07:03PM
To add a few comments to what others have written which may be of interest -- and like others I'm a physicist but no expert on quantum mechanics -- it seems that the "theory" that's going unnamed in the summary is Bohmian mechanics. An extremely important point to make about this is that Bohmian mechanics is observationally indistinguishable from quantum mechanics -- one can very easily turn one into the other. A way of finding Bohmian mechanics is to take the Schroedinger form of quantum mechanics, which is effectively based on a (complex) diffusion equation for a wavefunction, and split the wavefunction up into an amplitude and a phase. (The so-called Madelung representation, psi = A exp(iS), where both A and S are real numbers.) Following this through quickly leads to two equations. One is simply fluid continuity, which states that the density of a fluid is conserved; that density is A^2. The other is an equation for S, which can be interpreted as a Bernoulli equation (or, more obscurely but more usefully theoretically, a Hamilton-Jacobi equation). From this equation we can identify the potential that this fluid is moving in -- and it's modified from the classical situation purely and only by a non-local term depending on the derivatives of the density which is sometimes dubbed "the quantum potential".
Viewed in this representation, this "quantum potential" is the only difference between quantum mechanics and classical mechanics.
Bohmian mechanics is ultimately an interpretation that takes this seriously: start with a classical situation, postulate the quantum potential through some rapid hand-waving, and if you choose to work with a wavefunction combining together your Bernoulli equation and your continuity equation then that's your lookout. (A consequence of developing this fully is that Bohmian mechanics is a hidden-variable theory.) The more usual interpretation is that this is an interesting and sometimes useful curiosity.
http://plato.stanford.edu/entries/qm-bohm/ [stanford.edu] might be of interest to some -- section 5 is effectively what I've tried to describe here. It's also discussed on Wikipedia, http://en.wikipedia.org/wiki/De_Broglie%E2%80%93Bohm_theory#Derivations [wikipedia.org]