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    Including decoherence in the quantum mechanical descripti... — Carmelics
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    Including decoherence in the quantum mechanical description does not dissolve the measurement problem — the composite system of electron, apparatus, and environment is still left in a superposition of distinct outcome states.

    Modality & Possibility
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    Reasons For

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    • 1.Decoherence describes interactions in which differently localised states of the apparatus couple to different states of the environment.
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    • 2.By the same linearity arguments that apply to the electron-apparatus system, the composite of electron, apparatus, and environment evolves into a superposition: one branch corresponding to the environment coupling to the apparatus registering spin +1/2, and another branch corresponding to the environment coupling to the apparatus registering spin -1/2.
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    • 3.Adding the environment to the description does not break the linearity of the Schrödinger equation, so superposition persists at the larger composite level.
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    Reasons Against

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    • 1.Decoherence produces a reduced density matrix for the apparatus that is diagonal in the pointer basis, making off-diagonal interference terms negligibly small.
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    • 2.For all practical purposes, a density matrix indistinguishable from a proper mixture of definite outcomes is physically equivalent to a classical probability distribution over those outcomes.
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    • 3.If no empirically accessible quantity can distinguish a superposition from a mixture, the 'remaining superposition' is operationally vacuous and cannot constitute a measurement problem.
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    Reason against 2 of 2
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    • 1.On the Everett interpretation, as developed by Deutsch and Wallace, decoherence defines the branching structure that determines what counts as a distinct classical world.
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    • 2.The measurement problem as traditionally stated presupposes a single definite outcome must be selected from the superposition, but this presupposition is itself a substantive interpretive commitment, not a logical necessity.
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    • 3.If decoherence explains why observers within each branch invariably experience definite outcomes, the claim that a 'measurement problem persists' merely reasserts the rejection of many-worlds rather than identifying a residual formal problem.
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    Topics

    Modality & PossibilityCausation

    Key Terms

    Composite system(quantum mechanics)
    Multiple things treated together as a single, interconnected whole—in this case, the electron, the measuring device, and the surrounding environment all considered as one system.
    Distinct outcome states(quantum mechanics)
    Different possible results that are clearly separate from each other; for example, 'the electron is here' versus 'the electron is there' are two distinct outcomes.
    Quantum mechanical description(quantum mechanics)
    The set of rules and math that physicists use to predict how tiny particles like electrons behave.
    Superposition(as used in quantum mechanics and the measurement problem)
    A quantum state where something exists in multiple different conditions at the same time until it's actually measured or observed.
    The measurement problem(quantum mechanics/philosophy of science)
    A major unsolved puzzle in quantum physics: when we measure a quantum particle, it seems to 'choose' a definite state, but the theory doesn't clearly explain how or why this happens.
    decoherence(Used to describe why macroscopic superpositions are not directly observed, and assessed here for whether it resolves the measurement problem.)
    A quantum mechanical process in which differently localised states of a measuring apparatus couple to different states of the surrounding environment, entangling the composite system and suppressing interference between branches.

    Connections

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    Consciousness & Mind1 linked

    Related

    Adding the environment to the description does not break the linearity of the Sc...By the same linearity arguments that apply to the electron-apparatus system, the...Decoherence describes interactions in which differently localised states of the ...

    Source

    AI-extracted1/3 agreementValid
    SEP: qm-decoherence
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    Indeed, what happens if we include decoherence in the description? Decoherence tells us, among other things, that plenty of interactions are taking place all the time in which differently localised states of the apparatus registering, say, different \(x\)-spin values of an electron couple to different states of the environment. But now, by the same arguments as above, the composite of electron, apparatus and environment will be a superposition of (i) a state corresponding to the environment coup
    Extraction notes

    Validity: Extracted via Max plan + API grounding/validity checks

    Details

    Decoherence produces a reduced density matrix for the apparatus that is diagonal...
    +5 moreShow less
    For all practical purposes, a density matrix indistinguishable from a proper mix...If decoherence explains why observers within each branch invariably experience d...If no empirically accessible quantity can distinguish a superposition from a mix...On the Everett interpretation, as developed by Deutsch and Wallace, decoherence ...The measurement problem as traditionally stated presupposes a single definite ou...

    Similar

    There are exactly three coherent responses to the quantum measurement ...83%Either the composite system of electron, apparatus, and environment is...81%De Broglie–Bohm theory can recover both quantum and classical phenomen...79%Applying the same strategy to decoherence yields a picture in which pa...78%
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