Macro objects and superposition of states

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Living macro objects, like cats and humans, primarily exist in mixed states due to decoherence, despite some molecular systems possibly being in quantum superpositions at any given moment. Superpositions are characterized by coherent states with defined phase relationships, while decoherence leads to the loss of this coherence. The discussion highlights the distinction between superpositions and mixed states, emphasizing that complete decoherence results in a mixed state. Additionally, there are technical issues regarding linking to external resources, which caused some confusion among participants. The conversation ultimately centers on the implications of quantum mechanics for understanding the states of living beings.
entropy1
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Is a living macro object, such as a cat or human being, in fact in a superposition of states?
(I am thinking about for instance the multiple-universe idea)
 
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entropy1 said:
Is a living macro object, such as a cat or human being, in fact in a superposition of states?
(I am thinking about for instance the multiple-universe idea)

At any given instant, there are probably a small number of individual systems at the molecular level in your body that are in quantum superpositions, however for the most part, people (or cats) have undergone decoherence, and are thus best described as being in mixed states. To learn about the distinction between superpositions and mixed states, try reading this: http://en.wikipedia.org/wiki/Mixed_state#Pure_and_mixed_states

The upshot is that superpositions are coherent, i.e. there is a well-defined phase relationship between the components of the state. Decoherence can be thought of as the process of degradation of the coherence. A superposition that undergoes complete decoherence ends up as a mixed state.
 
entropy1 said:
Is a living macro object, such as a cat or human being, in fact in a superposition of states?
(I am thinking about for instance the multiple-universe idea)
Any state is unique.
But some people do like destroy unique state in the superposition of other unique states of unliving abstract objects.
 
SpectraCat said:
At any given instant, there are probably a small number of individual systems at the molecular level in your body that are in quantum superpositions, however for the most part, people (or cats) have undergone decoherence, and are thus best described as being in mixed states. To learn about the distinction between superpositions and mixed states, try reading this: http://en.wikipedia.org/wiki/Mixed_state#Pure_and_mixed_states

The upshot is that superpositions are coherent, i.e. there is a well-defined phase relationship between the components of the state. Decoherence can be thought of as the process of degradation of the coherence. A superposition that undergoes complete decoherence ends up as a mixed state.

just realized that PF doesn't like links to wikipedia sections, so the link I posted above is broken (although it seemed to work fine when I previewed it) ... so check out the section on "Pure and Mixed States" at this link:http://en.wikipedia.org/wiki/Mixed_state
 
SpectraCat said:
just realized that PF doesn't like links to wikipedia sections,
Looks fine to me. You just have to click on it rather than try to copy-paste it.
 
Hurkyl said:
Looks fine to me. You just have to click on it rather than try to copy-paste it.

Yeah .. it works for me now too .. however just before I wrote that last post, I had clicked on a link to a wikipedia section in another thread, and I got the PF-version of the Not Found page. I thought "uh oh" and I came back here and tried my link from last night, and got the same message. However when I tried it again just now everything seems fine. Perhaps it is just some weird browser-PF-OS clash (I use FF 5.0 on Mac OS 10.5.8) that is exclusive to my machine.
 
Time reversal invariant Hamiltonians must satisfy ##[H,\Theta]=0## where ##\Theta## is time reversal operator. However, in some texts (for example see Many-body Quantum Theory in Condensed Matter Physics an introduction, HENRIK BRUUS and KARSTEN FLENSBERG, Corrected version: 14 January 2016, section 7.1.4) the time reversal invariant condition is introduced as ##H=H^*##. How these two conditions are identical?

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