On 8/20/2013 5:26 AM, smi...@zonnet.nl wrote:
Citeren meekerdb <meeke...@verizon.net>:
On 8/16/2013 4:57 PM, smi...@zonnet.nl wrote:
Citeren meekerdb <meeke...@verizon.net>:
On 8/15/2013 6:18 AM, smi...@zonnet.nl wrote:
Citeren meekerdb <meeke...@verizon.net>:
On 8/14/2013 6:41 PM, 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
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