How fat is Schrödinger’s cat?

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Schrödinger’s cat has a macroscopicity of 57.

Schrödinger’s cat has a macroscopicity of 57.

In recent years physicists have been placing ever-larger objects into states of quantum superposition – the curious state that Schrödinger’s cat finds itself in. Now, researchers in Germany have devised a way of quantifying just how macroscopic those objects are and how much ground still needs to be made up before cats and other familiar items can be held in two or more quantum states at the same time.
Erwin Schrödinger’s famous thought experiment involves a cat in a box that is simultaneously alive and dead until an observer looks at it. This is an extreme example of a quantum effect called superposition in which a physical system such as an atom or photon can exist in two or more quantum states until a measurement is made on it. While superposition is a regular feature of the microscopic world, it is never seen in our everyday lives. Some physicists think that this conundrum is resolved by quantum mechanics simply breaking down above a certain size scale. Others believe instead that the transition is more gradual, with it becoming increasingly difficult for larger quantum objects to remain in a superposition. This is because the effect of environmental noise on a quantum state is essentially the same as making a measurement.
Just how big is big?
To find out exactly how and where the quantum world ends and the classical one begins, physicists have been placing bigger and bigger objects into quantum superpositions. These include groups of atoms reaching different heights within an atomic “fountain”, and large molecules made to interfere with themselves in double-slit-like experiments. Currents of microamps have also been observed to flow in opposite directions around a superconducting circuit at the same time….
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Written by physicsgg

April 25, 2013 at 7:33 pm


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  1. Thanks for writing these fascinating posts. Could you explain what you mean by ‘environmental noise’?

    This article left me wondering if, instead of quantum mechanics breaking down at some size scale, we simply aren’t in a position to observe objects beyond a certain size until after their potential (dead cat or live cat) has been realized.

    Arlen Rutledge

    May 7, 2013 at 5:37 pm

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