Wave particle duailty, boundry between classic and the quantum world

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At what point does matter stop having the ability to function as both a particle and a wave?
In the early 1800s Thomas young created a double slit experiment, where light passed threw two slits and created an interference pattern. This meant light was both a particle and a wave. In 1961 Claus Jonsson repeated the experiment with electrons. First he shot electrons threw one slit getting a pattern of .. one slit. Then he shot them threw two slits expecting to get two slits but instead he got an interference pattern. This means matter itself has the ability to act as both a particle and a wave. He wondered how this was possible and set up an electron detector to see how this was happening and repeated the experiment. This time he got two slits. Matter acted as a particle again just by being observed.
Later this experiment was repeated with the same results with bucky balls made of 60 carbon atoms and then even later completed with a 240 atom object.
Most recent and the most interesting Andrew Cleland of the university of California witnessed a mechanical resonator on a macroscopic scale (big enough to be seen with the naked eye) in a state of superposition. Could this thin disc made of aluminium nitrate, consisting of around a trillion atoms, be a link between our classical and the quantum world of the weird?
 
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atyy
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These experiments are wonderful. But they probably do not address the foundations of quantum mechanics, since these experiments just seem to confirm quantum mechanics at larger and larger scales. We already have reason to believe that quantum mechanics applies at the very largest scales http://www.astro.ucla.edu/~wright/cosmo_04.htm.

But if they do detect a failure of quantum mechanics, then that would affect quantum foundations. Here is one proposal to test a theory that predicts deviations from quantum mechanics:

http://arxiv.org/abs/1405.2868
Optomechanical sensing of spontaneous wave-function collapse
Stefan Nimmrichter, Klaus Hornberger, Klemens Hammerer
 
  • #3
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At what point does matter stop having the ability to function as both a particle and a wave?
Well that's not the correct way of looking at it.

Really its not a particle or a wave or a particle and a wave - its quantum stuff.

See the FAQ:
https://www.physicsforums.com/showthread.php?t=511178

While the above is about photons its thrust is true for all particles. Indeed in Quantum Field Theory, which is our most advanced quantum formalism, to which QM is just an approximation, everything is a quantum field and that can't be viewed in such simplistic terms as a particle or a wave.

But to get to the thrust of your query there is no boundary between the classical and the quantum world - everything is quantum. But due to the phenomena of decoherence our everyday world appears classical. This is the modern resolution to the issue with the Copenhagen interpretation that divides the world into classical and quantum:
http://motls.blogspot.com.au/2011/05/copenhagen-interpretation-of-quantum.html

You will find a detailed discussion in Omnes book:
https://www.amazon.com/dp/0691004358/?tag=pfamazon01-20&tag=pfamazon01-20

Thanks
Bill
 
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