On Tuesday, December 5, 2017 at 12:26:58 AM UTC, Bruce wrote:
>
> On 5/12/2017 3:15 am, Bruno Marchal wrote:
> > On 01 Dec 2017, at 01:49, Bruce Kellett wrote:
> >> On 1/12/2017 8:57 am, Bruce Kellett wrote:
> >>> On 1/12/2017 4:21 am, Bruno Marchal wrote:
> >>>> On 29 Nov 2017, at 23:16, Bruce Kellett wrote:
> >>>> On 30/11/2017 2:24 am, Bruno Marchal wrote:
> >>>>>> On 29 Nov 2017, at 04:59, Bruce Kellett wrote:
> >>>>>>
> >>>>>>> I would suggest that there is no such world. Whether a coin
> >>>>>>> comes up head or tails on a simple toss is not a quantum event;
> >>>>>>> it is determined by quite classical laws of physics governing
> >>>>>>> initial conditions, air currents and the like.
> >>>>>>
> >>>>>> It depends. If you shake the coin long enough, the quantum
> >>>>>> uncertainties can add up to the point that the toss is a quantum
> >>>>>> event. With some student we have evaluate this quantitavely (a
> >>>>>> long time ago) and get that if was enough to shake the coin less
> >>>>>> than a minute, but more than few seconds ... (Nothing rigorous).
> >>>>>
> >>>>> That is a misunderstanding of quantum randomness. For the outcome
> >>>>> of a coin toss to be determined by quantum randomness, we would
> >>>>> have to have a single quantum event where the outcome was
> >>>>> amplified by decoherence so that it was directly entangled with
> >>>>> the way the coin landed. Schematically:
> >>>>>
> >>>>> |quantum event>|coin> = (|outcome A> + |outcome B>)|coin>
> >>>>> = (|outcome A>|coin heads> + |outcome B>|coin tails>)
> >>>>
> >>>> The coin is quantum.
> >>>
> >>> The coin is classical, consisting of something of the order of 10^22
> >>> atoms. Indeterminacy in position as given by the Heisenberg
> >>> Uncertainty Principle, is undetectably small.
> >>
> >> I think it is worth while to put some (approximate) numbers around
> >> this. The reduced Planck constant, h-bar, is approximately 10^{-27}
> >> g.cm^2/s. The Uncertainty Principle is
> >>
> >> delta(x)*delta(p) >= h-bar/2.
> >>
> >> For a coin weighing approximately 10 g and moving at 1 cm/s, the
> >> momentum is mv = 10 g.cm/s. Taking the momentum uncertainty to be of
> >> this order, the uncertainty in position, delta(x) is of the order of
> >> 10^{-28} cm. A typical atom has a diameter of about 10^{-8} cm, so
> >> the uncertainty in position is approximately 20 orders of magnitude
> >> less than the atomic diameter.
> >
> > I think that is enough to get the macroscopic superposition, as, like
> > I explained, you have to take into account not just the quantum
> > indeterminacy, + the classical chaos. You might need to shake for some
> > minutes.
>
> You could shake for longer than the age of the universe and you will
> still not convert quantum uncertainties and classical thermal motions
> into a macroscopic superposition. Do you know nothing about coherence?
> And the fact that coherent phases between the components are what
> separates a superposition from a mixture?
Are the phase angles of components of a superposition identical? If so, is
this the definition of coherence? TIA, AG
> Random quantum uncertainties
> and thermal motions are not coherent, so cannot form superpositions.
>
>
> >> That is why quantum uncertainties are irrelevant for macroscopic
> >> objects. Uncertainties do not add up coherently for macroscopic
> >> objects --
> >
> > Sure they do, unless you add continuous collapse, or something.
> > decoherence is only entanglement with the environment, that is
> > "contagion of the superposition".
>
>
> You are talking rubbish. As above, the uncertainties are not coherent so
> they cannot add up to form a superposition. Collapse has nothing to do
> with it. Decoherence is unitary interaction with the environment, so
> that the environment becomes entangled with the original superposition,
> but you have to start with a superposition -- that process does not make
> one!
>
> >> macroscopic objects act as a unit, and the HUP is irrelevant, even
> >> for small coins.
> >
> > I am not yet convinced.
> >
> > Bruno
>
> I think there are some basics of quantum mechanics over which you are
> very confused.
>
> Bruce
>
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