Citeren Quentin Anciaux <[email protected]>:
2013/8/21 meekerdb <[email protected]>
On 8/20/2013 5:26 AM, [email protected] wrote:
Citeren meekerdb <[email protected]>:
On 8/16/2013 4:57 PM, [email protected] wrote:
Citeren meekerdb <[email protected]>:
On 8/15/2013 6:18 AM, [email protected] wrote:
Citeren meekerdb <[email protected]>:
On 8/14/2013 6:41 PM, [email protected] 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...
Regards,
Quentin
Yes, that's a good way of explaining this.
Saibal
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