On 8/21/2013 3:57 AM, Quentin Anciaux wrote:
2013/8/21 meekerdb <meeke...@verizon.net <mailto:meeke...@verizon.net>>
On 8/20/2013 5:26 AM, smi...@zonnet.nl <mailto:smi...@zonnet.nl> wrote:
Citeren meekerdb <meeke...@verizon.net <mailto:meeke...@verizon.net>>:
On 8/16/2013 4:57 PM, smi...@zonnet.nl <mailto:smi...@zonnet.nl>
wrote:
Citeren meekerdb <meeke...@verizon.net
<mailto:meeke...@verizon.net>>:
On 8/15/2013 6:18 AM, smi...@zonnet.nl
<mailto:smi...@zonnet.nl> wrote:
Citeren meekerdb <meeke...@verizon.net
<mailto:meeke...@verizon.net>>:
On 8/14/2013 6:41 PM, smi...@zonnet.nl
<mailto:smi...@zonnet.nl> wrote:
I guess I don't understand that. You seem
to be
considering a simple case of amnesia - all
purely
classical - so I don't see how MWI enters
at all.
The probabilities are just ignorance
uncertainty.
You're still in the same branch of the
MWI, you
just don't remember why your memory was
erased
(although you may read about it in your
diary).
No, you can't say that you are in the same
branch. Just
because you are in the clasical regime doesn't
mean that
the MWI is irrelevant and we can just pretend
that the
world is described by classical physics. It is
only that
classical physics will give the same answer as
QM when
computing probabilities.
Including the probability that I'm in the same
world as before?
With classical I mean a single world theory where you
just
compute the probabilities based "ignorance". This
yields the
same answer as assuming the MWI and then comouting the
probabilities of the various outcomes.
If what you are aware of is only described by
your
memory state which can be encoded by a finite
number of
bits, then after a memory resetting, the state
of your
memory and the environment (which contains also
the rest
of your brain and body), is of the form:
"The rest of my brain"?? Why do you suppose that
some part
of my brain is involved in my memories and not
other parts?
What about a scar or a tattoo. I don't see that
"memory" is
separable from the environment. In fact isn't that
exactly
what makes memory classical and makes the
superposition you
write below impossible to achieve? Your brain is a
classical
computer because it's not isolated from the
environment.
What matter is that the state is of the form:
|memory_1>|environment_1> + |memory_2>|environment_2>+..
with the |memory_j> orthonormal and the |environment_j>
orthogonal. Such a completely correlated state will
arise due to
decoherence, the probabilities which are the squared
norms of
the |environment_j>'s are the probabilities. They
behave in a
purely classical way due this decomposition.
The brain is never isolated from the environment; if
project
onto an |environment_j> you always get a definite
classical
memory state, never a supperposition of different
bitstrings.
But it's not the case that projecting onto a ddefinite
memory
state will always yield a definite classical
environment state
(this is at the heart of the Wigner's friend thought
experiment).
I think Wigner's friend has been overtaken by decoherence.
While I
agree with what you say above, I disagree that the
|environment_i>
are macroscopically different. I think you are making
inconsistent
assumptions: that "memory" is something that can be "reset"
without
"resetting" its physical environment and yet still holding
that
memory is classical.
The |environment_i> have to be different as they are entangled
with
different memory states, precisely due to rapid decoherence. The
environment always "knows" exactly what happened. So, the
assumption is
not that the environment "doesn't know" what has been done
(decoherence
implies that the environment does know), rather that the the
person
whose memory is reset doesn't know why the memory was reset.
So, if you have made a copy of the memory, the system files
etc., there
is no problem to reboot the system later based on these copies.
Suppose
that the computer is running an artificially intelligent system
in a
virtual environment, but such that this virtual environment is
modeled
based on real world data. This is actually quite similar to how
the
brain works, what you experience is a virtual world that the
brain
creates, input from your senses is used to update this model,
but in the
end it's the model of reality that you experience (which leaves
quite a
lot of room for magicians to fool you).
Then immediately after rebooting, you won't yet have any
information
that is in the environment about why you decided to reboot. You
then
have macroscopically different environments where the reason for
rebooting is different but where you are identical.
But that's where I disagree - not about the conclusion, but about
the
possibility of the premise. I don't think it's possible to erase,
in the
quantum sense, just your memory. Of course you can given a drug
that erases
short term memory and so it may be possible to create a drug that
erases
long term memory too, i.e. induces amnesia. But what you require
is to
erase long term memory in a quantum sense so that all the
informational
entanglements with the environment are erased too. So I don't
think you can
be to the "erased memory" state you need.
Brent
But then, there is no problem restoring the original configuration of a
PC (e.g.
if it has been infected by a virus, the systme may have become
unrecoverable,
and you need to format the hard drive and install the OS). If the
computer where
running an AI then that AI would simply be "born again".
If the state of the mulitverse were such that there are two sectors
were this
happened with two different virusses the culprit of having to reset the
PC, then
from the point of view of the "born again AI", which virus caused the
problem is
not deternoned until it accesses that information.
The born again AI is a unique state that isn't different in any of the
two
possible histories, if not then you would still have traces of the
virus left
behind in the system.
Why should it matter that it was running an AI instead of some other
program? You
seem to be saying that any reset will produce uncertainty, because there is
some
other branch of the multiverse in which there was a reset for a different
reason. I
can only understand that in the context of the program as a Platonic entity
- so for
that entity, which world it is in is uncertain. Is that what you're saying?
Brent
ISTM that it is the same as FPI, to correctly predict your future after the reset, you
have to take in account all the branches where you are in the same memory state, those
branches may have different past (and of course future), hence both side after the reset
are uncertain... it's not that you can jump on one branch or another, it means you are
in all the branches that are consistent with your memory state...
But it seems to me that this reset is a magical, impossible operation. If the human brain
is a classical computer then that means it's computational state can be reset. But it also
means the its physical state can't be reset. The resetting operation itself, being a
classical operation, is irreversible because of decoherence into the environment. So the
environment has the information about the state leading up to the reset and the reset
operation. So when you say 'you' can find yourself on another branch, it's not clear what
'you' refers to. Apparently it would have to refer to an abstract computation (per Bruno,
I guess) that happened to go through the same state twice (due to the 'reset') in this
world AND also at least once in some other world. But if it went through that state in
some other world, there was already FPI even without the reset. Right?
Brent
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