On 12/10/2012 10:01 PM, Jason Resch wrote:
On Mon, Dec 10, 2012 at 1:35 PM, meekerdb <[email protected]
<mailto:[email protected]>> wrote:
On 12/10/2012 10:16 AM, Jason Resch wrote:
On Mon, Dec 10, 2012 at 10:30 AM, meekerdb <[email protected]
<mailto:[email protected]>> wrote:
On 12/10/2012 2:56 AM, Bruno Marchal wrote:
But why isn't "It's a probabilistic world and it obeys the Born rule."
a good
explanation. I'm all for finding a better explanation, i.e. a
deterministic
one. But simply postulating an ensemble of worlds to make the
probabilities
"deterministic" in arbitrary way doesn't strike me as any improvement.
It is, as it explains interference, without adding something not well
defined
(apparatus, observer) not obeying QM (like with the collapse needed to
get one
physical reality).
That sounds like prejudice against probabilistic theories. The
interference is
inherent in the complex Hilbert space states. The interference happens
in one
world. As Omnes says, you don't need 'collapse' you just need to
accept that
you have calculated probabilities. That's what probability means -
some state
is actualized and others aren't.
How does Omnes explain the EPR experiment without collapse? It seems you
need to
give up not only determinism, but also locality.
Also, what do you think Omnes would predict as the outcome for Deutsch's
proposed
experiment:
In Deutsch's thought experiment, an atom, which has a determinate spin
state in
one axis, 'left' for example, is passed through a Stern-Gerlach
apparatus which
has the possibility of measuring it in another axis, as either spin
'up' or
spin 'down' in this case. This means that the atom is then in a
superposition
of 'up' and 'down' states from the perspective of an observer who has
not yet
become entangled with it. This superposition travels to the AI's
artificial
'sense organ'. Here it is provided with two options, it may be detected
as
either spin 'up' or spin 'down'. The AI's conscious mind then records
the
result. The collapse approach predicts that this will cause the atom to
collapse into one determinate state, with either a determinate 'up' or
'down'
(but not 'left' or 'right') spin. The Everett approach predicts that
the mind
will branch into two, one mind will record up and one down (but neither
will
record 'left' or 'right').
The whole process is then reversed so that the atom emerges from the
entrance
to the Stern-Gerlach apparatus and the mind forgets which result it
recorded.
This process does not erase any of the AI's other memories however,
including
the memory that they did record the atom to be in a definite state. If a
'left-right' detector was placed at the entrance of the Stern-Gerlach
apparatus
then the collapse approach predicts that it will be detected as being
in either
a 'left' or 'right' state with equal probability.
I think it is wrong in saying that the erasure of which-way information
(which I
think is actually impossible for a consciousness, artificial or otherwise)
will
leave the atom in an up/down state.
Isn't that exactly what the quantum erasure experiment shows?
Quantum erasure requires that the which-way information be eliminated from the world.
Once an AI consciousness gets the result I think that implies entanglement with the world
and after that the result can't be quantum erased. I know Deutsch supposes a quantum
computer AI can 'know' there was which-way information even though the which-way
information was quantum erased. But I find that doubtful. And even if it's true, the
'reversal' may bring the atom back to 'left'.
Why do you think it is impossible for a conscious process learn the result and then have
that result erased as in the quantum eraser experiment?
Because I think consciousness must be quasi-classical. Consciousness needs stable memory
and it needs to interact with its environment - together I think that implies it must be
essentially classical as a computer. That's one of my reservations about Bruno's oft
repeated assertion that he has proven that matter doesn't exist. When pressed he allows
that it may exist, but only derivatively within the computations of the UD. But it seems
to me likely that it, or something very like it, must exist (derivatively of not) in order
that consciousness exist; that 'matter' is necessary for consciousness of a human kind to
exist.
You keep asking me about 'collapse', but Copenhagen's physical collapse is
not the
same as Omnes epistemic collapse.
I am sorry. I don't feel I have a good understanding of what the distinction
is.
Omnes looks at it as a mathematical operation used in predicting experimental results.
That means the 'collapse' is just a change in description, not a physical process.
Brent
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