Experiments probing the macroscopic limits of QM

In summary, these researchers are looking into possible limits to quantum mechanics with experiments that use different types of technology.
  • #36
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https://arxiv.org/abs/0711.3773

quantum theory is intrinsically nonlinear, and goes to the standard linear limit for microscopic objects. THe nonlinear theory goes to the classical limit for large objects, but departs from linear quantum mechanics for mesoscopic objects.

Because of the non-linearity, the lifetime of two superposed states is no longer infinite. It decreases as the number of atoms in the object under study increases, going from an astronomically large value for microsystems, to extremely small values for macrosystems. Thus somewhere in between, the superposition lifetime ought to be measureable in the laboratory.

For the micro-mirror of a billion atoms, the superposition lifetime is predicted to be about ten days. If the number of atoms in the mirror is increased a thousand fold, the lifetime of superposition comes down to about a thousand seconds.

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  • #37
physika said:
quantum theory is intrinsically nonlinear
Please name a nonlinear equation.
physika said:
and goes to the standard linear limit for microscopic objects
Where is this limiting procedure towards microscopic objects defined?

You can't just throw around assertions like that.
 
  • #38
mfb said:
You can't just throw around assertions like that.

Not mine.

Tejinder P. Singh.

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  • #39
physika said:
Not mine.

The speculative paper you linked is about quantum gravity, which is totally off-topic here. Quantum mechanics as is understood and experimentally verified right now is linear.
 
  • #40
physika said:
Not mine.

Tejinder P. Singh.
He didn't make the assertions you made.
 
  • #41
mfb said:
He didn't make the assertions you made.
.

Yes he did.

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  • #42
physika said:
Yes he did.

He didn't say that it is non-linear, but that it might be according to some speculative models he is discussing. It's a very big difference since, as I said before, we don't have any experimental evidence of non-linearity. Besides, just linking paper and then writing things like "quantum theory is intrinsically nonlinear" without any additional comments is not a good way to discuss. For me it looks like spreading misinformation.
 
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  • #43
weirdoguy said:
linking paper and then writing things like "quantum theory is intrinsically nonlinear"

It is not my writing, it was he who wrote it..
 
  • #44
physika said:
it was he who wrote it.

He did not as I've already explained. Stop misstating this paper.
 
  • #45
I actually thought the revival of this thread was going to mention a new experiment... sadly, not. Disappointing.
 
  • #46
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https://www.uibk.ac.at/newsroom/13-million-euros-for-basic-quantum-research.html.en

"The Austrian-based quantum physicists Oriol Romero-Isart and Markus Aspelmeyer, together with Lukas Novotny and Romain Quidant from ETH Zurich, will receive one of the prestigious ERC Synergy Grants. Together they want to explore the limits of the quantum world by positioning a solid-state object containing billions of atoms at two locations simultaneously for the first time.

In answering this question, the Austrian-Swiss research team, supported by the EU’s Synergy Grant, now wants to take a big step forward. “We want to put a nanoparticle consisting of billions of atoms into a large superposition state,” says project coordinator Oriol Romero-Isart from the Department of Theoretical Physics at the University of Innsbruck and the Institute of Quantum Optics and Quantum Information (IQOQI) of the Austrian Academy of Sciences, describing their common goal."https://cordis.europa.eu/project/id/951234

"Q-Xtreme will bring macroscopic quantum physics to an entirely new level by preparing macroscopic quantum superpositions of objects containing billions of atoms, pushing current state-of-the-art by at least five orders of magnitude in mass.

This goal will be achieved by using a radically new approach: quantum controlling the center-of-mass motion of a levitated nanoparticle (a solid-state object of few hundred nanometers) in ultra-high vacuum by using optical, electrical and magnetic forces. Q-Xtreme requires cutting-edge expertise in photonics, nanotechnology, optoelectronics, and quantum technology, which this Synergy Group uniquely combines. The achievements of Q-Xtreme are only possible by the combined proficiency in both fundamental science and engineering of this Synergy Group."
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  • #47
https://phys.org/news/2021-06-physicists-human-scale-standstill-quantum-state.html

Now for the first time, scientists at MIT and elsewhere have cooled a large, human-scale object to close to its motional ground state. The object isn't tangible in the sense of being situated at one location, but is the combined motion of four separate objects, each weighing about 40 kilograms. The "object" that the researchers cooled has an estimated mass of about 10 kilograms, and comprises about 1x1026, or nearly 1 octillion, atoms.

Paper: https://science.sciencemag.org/content/372/6548/1333
 
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