This all assumes that photons, electrons, etc. are real. We don't know that.
If you were Einstein, and you were faced with Bell's result, you could have
concluded that the nonexistence of local hidden variables implies that
elementary paricles don't exist. They are mere mathematical tools to compute
the outcome of experiments. The real underlying theory of Nature could be
still be deterministic. Recently 't Hooft has shown how QM can emerge out of
a deterministic theory. In this case QM has to be interpreted according to
the Copenhagen interpretation.


----- Oorspronkelijk bericht -----
Van: "Bruno Marchal" <[EMAIL PROTECTED]>
Aan: "scerir" <[EMAIL PROTECTED]>
CC: <[EMAIL PROTECTED]>
Verzonden: vrijdag 12 juli 2002 12:44
Onderwerp: Re: "Morality" in a Block Multiverse


> Hi Serafino,
>
> At 23:00 +0200 10/07/2002, scerir wrote:
> >  > Hal
> >>  You can also have a "block universe" in QM with the many-world
> >>  interpretation.  It has a more complicated geometric structure but
> >>  philosophically it is deterministic, with the same issues regarding
> >>  changes, free will, etc.
> >
> >I'm not an Everettista, anyway let us try. Alice has photon 1, which is
in a
> >certain quantum state, unknown to Alice and unknown to anyone else.
> >Let us say that this unknown quantum state is
> >|psi>_1 =  a |0>_1 + b |1>_1
> >with |a|^2 + |b|^2 = 1
> >and where |0>_1 and b |1>_1 represent two orthogonal quantum states
> >and a and b represent complex amplitudes.
> >
> >Now Alice wants to "transfer" (I say: "transfer") her quantum state to
Bob,
> >which is remote, so she can not directly deliver it to him. But,
fortunately,
> >Alice also has a pair of entangled photons, let us say the photon 2 and
the
> >photon 3, and she already gave the photon 3 to Bob, who still has
> >this particle.
> >Leaving apart normalization factors we can write that the total
> >state of those 3
> >photons is
> >|psi>_1,2,3 =
> >( |0>_1 |1>_2 - |1>_1 |0>_2 )    (- a |0>_3 - b |1>_3 ) +
> >( |0>_1 |1>_2 + |1>_1 |0>_2 )   (- a |0>_3 + b |1>_3 )  +
> >( |0>_1 |0>_2 - |1>_1 |1>_2 )    ( a |1>_3 + b |0>_3 )  +
> >( |0>_1 |0>_2 + |1>_1 |1>_2 )   ( a |1>_3 - b |0>_3 )
> >
> >Alice now performs a measurement on photons 1 and 2 and she "projects"
her
> >two photons onto one of these four states below:
> >( |0>_1 |1>_2 - |1>_1 |0>_2 )
> >( |0>_1 |1>_2 + |1>_1 |0>_2 )
> >( |0>_1 |0>_2 - |1>_1 |1>_2 )
> >( |0>_1 |0>_2 + |1>_1 |1>_2 )
> >
> >And consequently Bob will found his photon in one of these four states
below
> >(- a |0>_3 - b |1>_3 )
> >(- a |0>_3 + b |1>_3 )
> >( a |1>_3 + b |0>_3 )
> >( a |1>_3 - b |0>_3 )
> >
> >Now Alice, who wants to "transfer" the unknown quantum state of photon 1
to
> >Bob, must inform Bob, via a classical channel, about her measurement
> >("projection")
> >result (on photons 1 and 2). So Bob can perform (25% of times it is not
> >required)
> >the right simple unitary transformation on his photon 3, in order to
> >obtain the
> >initial
> >quantum state  |psi>_1 =  a |0>_1 + b |1>_1
> >
> >Note that Alice does not get any information, from her measurement, about
the
> >quantum state she wants to "transfer" and about the values of those a and
b
> >amplitudes. Note also that during Alice's measurement photon 1 loses his
> >original quantum state, as required by the no-cloning theorem.
> >
> >Ok, that was the basic teleportation (= trasportation) of a quantum state
from
> >Alice to Bob.
> >
> >Now something strange happens in the MWI version. Alice's measurement
does not
> >"project" the superposition of
> >( |0>_1 |1>_2 - |1>_1 |0>_2 )
> >( |0>_1 |1>_2 + |1>_1 |0>_2 )
> >( |0>_1 |0>_2 - |1>_1 |1>_2 )
> >( |0>_1 |0>_2 + |1>_1 |1>_2 )
> >onto just one of these quantum states (above). They all exist. And all
these
> >quantum
> >states (below) also exist
> >(- a |0>_3 - b |1>_3 )
> >(- a |0>_3 + b |1>_3 )
> >( a |1>_3 + b |0>_3 )
> >( a |1>_3 - b |0>_3 )
> >and one of them (1 over 4 = 25% of times) is the same quantum state that
Alice
> >wanted to "transfer" to Bob.
> >
> >Thus it seems that in the MWI of teleportation the quantun state it is
not
> >"teleported" or "trasported" but it is already "there", and it is already
> >"there", in one of those branches, from the beginning. This stuff
> >reminds me of
> >the "block universe", at least a bit.
> >
> >s.
> >
> >[still not an Everettista] :-)
>
>
>
> Still not? Even after this nice presentation of (quantum) teleportation
> in the MW view? Your last remark confirms my feeling that quantum
information
> is "just" classical information about which partition of the multiverse
> we belong (and measurement is always sort of self-localisation).
> Do you know the paper by Peres http://xxx.lanl.gov/abs/quant-ph/9904042
> Peres shows how to teleport entanglement in the past! In the MW view there
> is no problem at all, neither non-locality, nor 3-indeterminacy. But Peres
> concludes its paper by insisting on keeping the Copenhague view. It's
> quite mysterious.
> If you have time to look at it I would appreciate your opinion.
>
> Bruno
>
>


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