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.
Saibal
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