From: <[email protected] <mailto:[email protected]>>

On Tuesday, June 5, 2018 at 1:18:29 AM UTC, Bruce wrote:

    From: <[email protected]>

    Remember that the analysis I have given above is schematic,
    representing the general progression of unitary evolution. It is
    not specific to any particular case, or any particular number of
    possible outcomes for the experiment.

    Bruce

    *OK. For economy we can write, **(|+>|e+> + |->|e->),  where e
    stands for the entire universe other than the particle whose spin
    is being measured. What is the status of the interference between
    the terms in this superposition? For a quantum superposition to
    make sense, there must be interference between the terms in the
    sum. At least that's my understanding of the quantum principle of
    superposition. But the universe excluding the particle being
    measured seems to have no definable wave length; hence, I don't
    see that this superposition makes any sense in how superposition
    is applied. Would appreciate your input on this issue. TIA, AG*

    A superposition is just a sum of vectors in Hilbert space. If
    these vectors are orthogonal there is no interference between
    them. Your quest for a wavelength in every superposition is the
    wrong way to look at things. Macroscopic objects have vanishingly
    small deBroglie wavelengths, but the can still be represented as
    vectors in a HIlbert space, so can still form superpositions. I
    think you are looking for absolute classicality in quantum
    phenomena -- that is impossible, by definition.

    Bruce


*If that's the case, why all the fuss about Schrodinger's cat? AG*

Is there a fuss about Schrödinger's cat? Whatever fuss there is, is not about the possibility of a superposition of live and dead cats. It is about choosing the correct basis in which to describe the physical situation. The Schrödinger equation does not specify a basis, and that is its main drawback. In fact, that observation alone is sufficient to sink the naive many-worlds enthusiast -- he doesn't know in which basis the multiplication of worlds occurs.

Bruce

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