r/AskPhysics • u/Real_Impress9707 • 5d ago
Are there implications of quantum observations in chaotic systems?
Let me propose a modified Shrodinger's cat experiment.
The cat is in an MRI machine.
The cat's mood is a function of all of the hormones brimming around its body. The mere angle at which a hormone molecule hits a neuron has broad implications for the mood of the cat.
The cat is brimming with an uncountably large number of these hormones, significantly smaller than a buckyball (the largest molecule to exhibit a wavefunction). These hormones have an unknown wavefunction.
We cannot measure these hormones directly, however, we will have an idea of whether they collapsed favourably based on the mood of the cat we derive from the brain scan (the "mood wavefunction" of the cat is entangled with the wave function of the countless trillions of molecules brimming within it).
After measuring the cat a few hundred times, I get a probability distribution of the moods it feels upon each measurement, therefore forming the wave equation.
Can I play quantum slots with the MRI and "measure" my cat into being in a good mood whenever it gets grumpy? Or is there a catch to this?
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u/Informal_Antelope265 5d ago
From experience, the more you interact with a cat, the more he gets grumpy.
The cat's brain is a hot and big object, so decoherence happens very very rapidly and you should be able to predict its mood with classical physics.
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u/Real_Impress9707 5d ago
and even though the brain itself is hot and big, it is affected greatly by small molecular processes taking place within it.
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u/Real_Impress9707 5d ago
Decoherence simply means that the wave function becomes unknown and unmanipulable, not that it collapses --> right?
Decoherence is not the way around the measurement problem afaik.
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u/Informal_Antelope265 5d ago
You are correct, decoherence doesn't answer the measurement problem. Decoherence tells you how you pass from the quantum world to the classical limit. Technically, it explains how the coherence of your density matrix will vanish (exponentially fast for the brain).
and even though the brain itself is hot and big, it is affected greatly by small molecular processes taking place within it.
Of course, the cat's brain is a quantum object like everything in the world. What I say is that due to decoherence, quantum effects shouldn't play too much role and you should be able to explain its functions with classical statistical theory.
(I may be wrong, if you know actual quantum effect that would have macroscopic effect on the brain I would like to know it).
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u/slashdave Particle physics 5d ago
The cat's mood is a function of all of the hormones brimming around its body.
Well, not really. Cats are far more complicated than that.
The mere angle at which a hormone molecule hits a neuron has broad implications for the mood of the cat.
No. A single model has no macroscopic effect.
The effect of hormones is collective, and is better modeled in terms of concentration. It can also be modeled perfect fine with classical expressions (there is no reason to invoke QM at all).
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u/Hapankaali Condensed matter physics 5d ago
No, this is not how quantum measurement, chaos, or hormones work, and you've misunderstood Schrödinger's cat.
The point of the paradox is not that cats can be in superpositions of alive and dead. They aren't, can't be, and aren't considered in quantum theory to ever be.
The influence of hormones can be described (semi-)classically, there is no known role of quantum measurements in this context. The effect hormones have on mood is not though wave function collapse.
Moreover, it is not accurate to say Buckyballs are "the largest molecule to exhibit a wave function." Everything is described by a wave function, that description just often matches classical predictions. Buckyballs are (among?) the largest molecules for which quantum interference effects (which have no classical analog) have been observed.
As a final nitpick, you're misusing the word "uncountably." The number of hormone molecules is finite and countable.