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Macro quantum effects? Answered

A permanent magnet's magnetism is commonly described as a small molecular effect wherein the the effect of individual molecules is polarised in a way so that the effect reinforces and creates a macro effect throughout the entire material. Is it possible - do you know of any surfaces or materials, real or proposed, that could be considered to be a similar kind of "upscaling of 'microscopic' properties"?

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westfw (author)2009-02-26

There's a device analagous to a permanent magnet that produces a permanent ELECTRICAL field, called an "electret."

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PKM (author)westfw2009-02-27

Isn't something creating a permanent electrical field a charged object? If I rub a balloon against my synthetic fleece and then somehow stop it leaking charge to the rest of the world it has a permanent electrical field, but that's not a quantum effect. IIRC gecko feet stick because they are covered in tiny tiny tiny protrusions that get so close to a surface they are attracted by Van der Waals forces, the force that keep molecules in solid substances together.

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kelseymh (author)2009-02-26

Yes, it's possible, and there are both existing examples and proposed experiments.

Just this morning, I posted one abut making two-photon entanglement visible to the naked eye.

Bose-Enstein condensates are systems of a large number of atoms (tens of thousands to millions!) which have been cooled to a sufficiently low temperature that they are all in their ground state. Such a system behaves like a single wavefunction, not like a "collection of atoms".

Quantum dots are "mesoscopic" objects -- solid pieces made of millions or tens-of-millions of atoms -- whose structure has been tuned to have a series of well-separated energy levels. They behave like "artificial atoms" with emmission and absoption spectra, "quantum jumps" and all the other features normally associated with atomic physics.

Superconductivity itself is an example of a macroscopic quantum phenomenon. The BCS theory describes it as the formation of Cooper pairs of spin-antialigned electrons at long range, and subsequent B-E condensation of those pairs into a collective.

I could probably go on coming up with examples, but reading the Wikipedia articles on those three topics should keep you occupied for a while :-)

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