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What are some good examples? For example, chaotic systems where you can show that quantum nondeterminism sets the initial conditions.

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closed as not constructive by Manishearth, David Z Jun 28 '12 at 16:06

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If you believe in decoherence the is no quantum non-determinism any more than chaotic systems are non-deterministic. There is just insufficient knowledge of all the degrees of freedom. – John Rennie Jun 28 '12 at 8:03
"If you believe in decoherence there is no quantum non-determinism" - that is not true; decoherence is wavefunction dynamics and is independent of interpretation. Anyway, this is not a question about quantum ontology. I am looking for concrete examples of physical systems in which macroscopic outcomes are the result of quantum events. This is true for measuring devices, for example, but those aren't natural systems... The question is in response to – Mitchell Porter Jun 28 '12 at 8:46
Schrodingers' cat? I don't mean the superposition side of the idea, just the fact that the cat may survive or may be killed as a result of a tunnelling probability in the uranium nucleus. All macroscopic behaviour is the result of quantum events, so I don't really understand what you're asking for. – John Rennie Jun 28 '12 at 8:54
Schrodinger's cat would be an example, where you have two or more macroscopically distinct outcomes with a quantum cause. But it's an artificial setup. I want examples from nature. If you follow the link, the guy is asking for situations where distinct quantum outcomes show up in the mesoscopic world. Radioactive decay would be an example, but there has to be something more striking than that. – Mitchell Porter Jun 28 '12 at 9:20
The blog is trying to relate Obama being relected to a quantum event, but that's like trying to relate the function of a car engine to the motion of a single oxygen molecule. The butterfly's wing is a nice analogy, but that isn't how statistical mechanics works. In the macroscopic world individual quantum events are washed out. It's only in artifical setups like the Schrodingers' cat that you'll see an effect from an individual quantum event. – John Rennie Jun 28 '12 at 9:26