What is Macroscopic quantum: Definition and 14 Discussions

Macroscopic quantum phenomena are processes showing quantum behavior at the macroscopic scale, rather than at the atomic scale where quantum effects are prevalent. The best-known examples of macroscopic quantum phenomena are superfluidity and superconductivity; other examples include the quantum Hall effect, giant magnetoresistance and topological order. Since 2000 there has been extensive experimental work on quantum gases, particularly Bose–Einstein condensates.
Between 1996 and 2016 six Nobel Prizes were given for work related to macroscopic quantum phenomena. Macroscopic quantum phenomena can be observed in superfluid helium and in superconductors, but also in dilute quantum gases, dressed photons such as polaritons and in laser light. Although these media are very different, they are all similar in that they show macroscopic quantum behavior, and in this respect they all can be referred to as quantum fluids.
Quantum phenomena are generally classified as macroscopic when the quantum states are occupied by a large number of particles (of the order of the Avogadro number) or the quantum states involved are macroscopic in size (up to kilometer-sized in superconducting wires).

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  1. Kinker

    I Does gravity cause quantum decoherence?

    Does gravity cause quantum decoherence? In the microscopic world, gravity seems to act weakly, but in the macroscopic world, it seems to act strongly. Is this the boundary between the microscopic world and the macroscopic world? So a phenomenon like quantum tunneling can occur in the microscopic...
  2. S

    I Macroscopic quantum entanglement?

    Very confused about this article and the experiment it's based on. I'm not very knowledgeable on this, but I'm very confused on what's happening here. It seems extremely weird to me
  3. S

    I What did Omnès mean with this?

    Summary: What did Omnès mean with this? I found an old article by Roland Omnès which analyzes the EPR paradox and offers a solution to it (https://www.sciencedirect.com/science/article/abs/pii/0375960189900182). At some point, the article says: "Some macroscopic systems do not satisfy the...
  4. A

    The effect of macroscopic quantum phenomena on human evolution

    In a discussion between Sam Harris and Brian Greene, at this point, Brian stated that even if we return the brain and all the environment to its previous state, we "WON'T MAKE THE SAME NOISES"; I know that for example, indeterminacy in determining the precise time of decay of an atom (and the...
  5. Auto-Didact

    A Experiments probing the macroscopic limits of QM

    This thread is to serve as both a compilation and ground of discussion of key experiments, both historical and planned, which attempt to probe possible macroscopic limits of QM, taking into account e.g. some particular gravitational/optical/mechanical/superconducting/etc aspect and/or...
  6. Auto-Didact

    A Weinberg: detecting changes to QM using atomic clocks

    Steven Weinberg has lately been critical of QM. He now also has a technical paper out called 'Lindblad Decoherence in Atomic Clocks', available on arxiv. Here is the abstract: It's a short paper (6 pgs of text), arguing for objective collapse (a la GRW/Diosi-Penrose/etc) instead of...
  7. D

    Everett's interpretations and Macroscopic quantum states

    Max Tegmark in his paper “Many worlds in context” http://arxiv.org/abs/0905.2182 Argues that …. .“Everett’s MWI is simply standard QM with the collapse postulate removed, so that the Schrödinger equation holds without exception”. He also argues that from this we can deduce that not only...
  8. S

    The arguments against macroscopic quantum states are

    I am aware and well read on the decoherence approach to understanding how conglomerations of micro quantum systems will tend to lose quantum coherence via interaction with the environment. The cross terms in the density matrix for the system will tend to zero (due to the partial trace...
  9. StevieTNZ

    Macroscopic Quantum Coherence & Macrorealism experiments

    Has anyone performed experiments regarding macroscopic quantum coherence (superposition of and macroscopic object)? What about testing if macroscopic objects obey macrorealism, or whether QM prevails? Links to articles or experiments would be apprecited.
  10. Truecrimson

    Macroscopic quantum effects and gravitational wave detector

    My first thread here. Please bear with my lack of knowledge. I talked to a physics grad student about whether it's fair to describe QM as a theory applied only to microscopic objects. Although the definition of "fair" is ambiguous, at least he told me that, from his understanding, he wouldn't...
  11. K

    The Significance of Decoherence in the Quantum-to-Classical Transition

    I read often that the transition from quantum to classical, the fact that there normally no macroscopic quantum objects are observed, has only become clear with the proper understanding of the decoherence mechanism. But what about Broglie wavelength!? Physicists knew before, that macroscopic...
  12. C

    Is this a valid example of macroscopic quantum behavior?

    In some discussions here about quantum effects in the macro world, ZapperZ will only admit that things like superconductivity, Bose Einstein condensates etc. are good examples. But these are just macroscpic quantum coherent phenomena. Of course, if you have a flux qubit, you can directly...
  13. B

    Does Quantum Mechanics Apply to All Scales of Reality?

    I have heard many times that's quantum mechanics doesn't apply at the macroscopic level. But I am not sure if I fully understood what was meant. Surely quantum mechanics applies even to macroscopic objects, its just that the wavefunction of such objects is so highly localized that we in effect...
  14. D

    Macroscopic quantum model

    [SOLVED] Macroscopic quantum model Hi! I'm supposed to calculate the quantum number of a macroscopic system (The Earth and a satellite). I should assume that the satellite is moving in a circular motion around earth, and that it fulfills the same quantization conditions as the Bohr model...