2013/8/21 meekerdb <meeke...@verizon.net>

> 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

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...


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