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Macroscopic quantum phenomena
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<p>Macroscopic quantum phenomena are processes showing <a href="/facts/Quantum_mechanics/BRc3Mzgr">quantum behavior</a> at the <a href="/facts/Macroscopic_scale/NLwPDtLe">macroscopic scale</a>, rather than at the <a href="/facts/Atom/FoQ4kGN5">atomic scale</a> where quantum effects are prevalent. The best-known examples of macroscopic quantum phenomena are <a href="/facts/Superfluidity/QuePDujN">superfluidity</a> and <a href="/facts/Superconductivity/pqQAlSzJ">superconductivity</a>; other examples include the <a href="/facts/Quantum_Hall_effect/yK3zcCgu">quantum Hall effect</a>, <a href="/facts/Josephson_effect/2fvcdS8N">Josephson effect</a> and <a href="/facts/Topological_order/EfEnKRSw">topological order</a>. Since 2000 there has been extensive experimental work on quantum gases, particularly <a href="/facts/Bose%25E2%2580%2593Einstein_condensate/76peCwfW">Bose–Einstein condensates</a>. </p><p>Between 1996 and 2016 six <a href="/facts/Nobel_Prize/3z1Y3oFL">Nobel Prizes</a> were given for work related to macroscopic quantum phenomena. Macroscopic quantum phenomena can be observed in <a href="/facts/Superfluid_helium/yRul93TG">superfluid helium</a> and in <a href="/facts/Superconductors/pqQAlSzJ">superconductors</a>, but also in dilute quantum gases, <a href="/facts/Dressed_particle/I1p9t7wz">dressed photons</a> such as <a href="/facts/Bose%25E2%2580%2593Einstein_condensation_of_polaritons/eWLb2oEG">polaritons</a> and in <a href="/facts/Laser/jk6PTvvT">laser</a> 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 <a href="/facts/Quantum_fluid/bFHpunBN">quantum fluids</a>. </p><p>Quantum phenomena are generally classified as macroscopic when the quantum states are occupied by a large number of particles (of the order of the <a href="/facts/Avogadro_number/SwajCq22">Avogadro number</a>) or the quantum states involved are macroscopic in size (up to kilometer-sized in <a href="/facts/Superconducting/pqQAlSzJ">superconducting</a> wires). </p>