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>)
This direct entanglement is not reproduced by the sum over many random
quantum events where the ensuing entanglement is extremely complicated,
with no direct connection between a quantum outcome and the result of
the toss. Such accumulation of quantum uncertainties is similar to
simple thermal noise, and could not be distinguished from it.
Bruce
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