On 30 May 2017 at 14:48, Bruno Marchal <marc...@ulb.ac.be> wrote:
>
> On 30 May 2017, at 14:10, Telmo Menezes wrote:
>
> On Tue, May 30, 2017 at 1:35 PM, Bruno Marchal <marc...@ulb.ac.be> wrote:
>>
>>>
>>> On 30 May 2017, at 11:28, Telmo Menezes wrote:
>>>
>>> On Tue, May 30, 2017 at 3:47 AM, Pierz <pier...@gmail.com> wrote:
>>>>
>>>>>
>>>>>
>>>>>
>>>>> On Tuesday, May 30, 2017 at 9:14:07 AM UTC+10, Bruce wrote:
>>>>>
>>>>>>
>>>>>>
>>>>>> On 29/05/2017 11:21 pm, Telmo Menezes wrote:
>>>>>>
>>>>>>>
>>>>>>> On Mon, May 29, 2017 at 3:06 PM, Bruce Kellett
>>>>>>> <bhke...@optusnet.com.au> wrote:
>>>>>>>
>>>>>>>>
>>>>>>>> On 29/05/2017 10:42 pm, Telmo Menezes wrote:
>>>>>>>>
>>>>>>>>>
>>>>>>>>> On Mon, May 29, 2017 at 2:26 PM, Bruce Kellett
>>>>>>>>> <bhke...@optusnet.com.au> wrote:
>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> On 29/05/2017 6:26 pm, Telmo Menezes wrote:
>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> On Mon, May 29, 2017 at 3:26 AM, Bruce Kellett
>>>>>>>>>>> <bhke...@optusnet.com.au> wrote:
>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>> I would say that there is only one history leading to our
>>>>>>>>>>>> present
>>>>>>>>>>>> state.
>>>>>>>>>>>> Whether you take an MWI view or a collapse view, the wave
>>>>>>>>>>>> function
>>>>>>>>>>>> branches
>>>>>>>>>>>> deterministically at every point, so if you follow your current
>>>>>>>>>>>> twig
>>>>>>>>>>>> back
>>>>>>>>>>>> down to the main trunk etc, there will be a unique path.
>>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> I don't think we can say we are in a specific twig. Many things
>>>>>>>>>>> about
>>>>>>>>>>> out present state are unknown/undefined. I can imagine that there
>>>>>>>>>>> are
>>>>>>>>>>> many well-defined present states that are compatible with my
>>>>>>>>>>> current
>>>>>>>>>>> subjective state.
>>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> Sure, but we are talking about wave functions, not subjective
>>>>>>>>>> states.
>>>>>>>>>>
>>>>>>>>>
>>>>>>>>> Replace "subjective" with "incomplete knowledge".
>>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> Doesn't help. Of course our knowledge is incomplete, the wave
>>>>>>>> function
>>>>>>>> isn't
>>>>>>>> completely known either -- but the result of specific measurements
>>>>>>>> are
>>>>>>>> what
>>>>>>>> is at stake here, and they are known quantum states.
>>>>>>>>
>>>>>>>
>>>>>>> In my view, what's at stake here is the possibility of latent
>>>>>>> variables having some degree of freedom leading to the same macro
>>>>>>> states (provided that there is incomplete information about these
>>>>>>> macro states, as is the case for humans).
>>>>>>>
>>>>>>
>>>>>>
>>>>>> I am still not clear about what you are trying to say. It is certainly
>>>>>> true that many internal details of your microscopic organization could
>>>>>> be changed and you wouldn't know the difference. For that matter, an
>>>>>> almost infinite number of details about the rest of the universe could
>>>>>> be different and you would still be the same. But that is not what we
>>>>>> were talking about. I understood the issue to be whether there was a
>>>>>> unique past, or whether several (or many) different paths lead to our
>>>>>> current state. The determinism of the Schrödinger equation would
>>>>>> suggest
>>>>>> that your unique state has a unique history. Variations in microscopic
>>>>>> details of with your body, or the universe, would correspond to
>>>>>> different decohered worlds with no overlap with our world. So while
>>>>>> such
>>>>>> variations are possible, they do not amount to multiple histories
>>>>>> leading to our current state. We don't need to know that state in
>>>>>> detail
>>>>>> to be able to argue the consequences of determinism.
>>>>>>
>>>>>> In fact you can perform a quantum erasure experiment, and be sure
>>>>>>>>>>> that
>>>>>>>>>>> your current state goes through at least two different shortest
>>>>>>>>>>> paths
>>>>>>>>>>> to the root, and it becomes nonsensical to say that one is the
>>>>>>>>>>> "correct" one. I don't think anyone knows how far this can go
>>>>>>>>>>> into
>>>>>>>>>>> the
>>>>>>>>>>> macroscopic world, but I don't see any reason to believe that it
>>>>>>>>>>> doesn't.
>>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> I don't understand what you think you are getting in a quantum
>>>>>>>>>> erasure
>>>>>>>>>> experiment. If the "which way" information that was gathered is
>>>>>>>>>> erased,
>>>>>>>>>> normal interference patterns are seen in the double slit
>>>>>>>>>> situation.
>>>>>>>>>> The
>>>>>>>>>> two
>>>>>>>>>> paths (through the separate slits) are in unresolved superposition
>>>>>>>>>> until
>>>>>>>>>> they hit the detector, when decoherence takes over. There are not
>>>>>>>>>> two
>>>>>>>>>> separate worlds, and your state is the result of the superposed
>>>>>>>>>> paths,
>>>>>>>>>> not
>>>>>>>>>> of either path separately. There is no ambiguity about which the
>>>>>>>>>> the
>>>>>>>>>> "correct" path -- neither is, both contribute equally.
>>>>>>>>>>
>>>>>>>>>
>>>>>>>>> I would say that the delayed choice version of the experiment makes
>>>>>>>>> it
>>>>>>>>> clear that there are two possible pasts that lead to the same
>>>>>>>>> present
>>>>>>>>> state -- they differ by one bit of information.
>>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> That is not what is implied by delayed choice quantum erasure.
>>>>>>>> Whether
>>>>>>>> an
>>>>>>>> interference pattern is seen or not is determined by whether the
>>>>>>>> "which
>>>>>>>> way"
>>>>>>>> information is erased or not. But whether it is or not, the
>>>>>>>> interference is
>>>>>>>> only seen when coincidence measurements tell one which photons to
>>>>>>>> count. And
>>>>>>>> the timing information necessary for coincidence determination is
>>>>>>>> available
>>>>>>>> only *after* all decisions about erasure or not have been made,
>>>>>>>> whether
>>>>>>>> that
>>>>>>>> decision is made before or after the other photon of the entangled
>>>>>>>> pair
>>>>>>>> has
>>>>>>>> reached its detector.
>>>>>>>>
>>>>>>>> "Delayed choice" is perhaps a misleading phrase in this context, and
>>>>>>>> it
>>>>>>>> does
>>>>>>>> not lead to an ambiguity of path -- it merely tells whether there
>>>>>>>> was
>>>>>>>> an
>>>>>>>> intact superposition or not.
>>>>>>>>
>>>>>>>
>>>>>>> I know, this is not what I am trying to say. I'll choose something
>>>>>>> much
>>>>>>> simpler:
>>>>>>>
>>>>>>> Suppose there is a computer running in an empty room. This computer
>>>>>>> is
>>>>>>> connected to a random number generator. At some point it uses the
>>>>>>> random value to decide if it's going to show a screen that is all
>>>>>>> green or all red. Nobody witnesses it.
>>>>>>>
>>>>>>
>>>>>>
>>>>>> If the random number generator is based on quantum randomness, then in
>>>>>> principle you will get a superposition of red and green screens, but
>>>>>> this is like the question as to whether we see a superposition of live
>>>>>> and dead cats in Schrödinger's thought experiment. Even if there is an
>>>>>> underlying quantum event that would give a superposition, decoherence
>>>>>> steps in and resolves the outcome into separate worlds long before we
>>>>>> reach the macro level of live/dead cats or red/green screens.
>>>>>> Decoherence does not require anyone to witness it....
>>>>>>
>>>>>
>>>>>
>>>>>
>>>>> I believe Telmo is subscribing to a view of QM, suggested by Bruno's
>>>>> "comp"
>>>>> theory, that the observer's subjective state - down to some unknown
>>>>> level
>>>>> of
>>>>> resolution (the "substitution level") - is what determines the possible
>>>>> future states of that observer (probabilistically, by the measure on
>>>>> subjective continuations in the UD trace).
>>>>>
>>>>
>>>>
>>>> I would say that I am assuming the computational theory of mind + MWI,
>>>> none of which are really Bruno's idea.
>>>>
>>>
>>>
>>> ?
>>>
>>> "my theory of mind" is (a weaker than usual) CTM. It implies all CTMs in
>>> the
>>> literature, which somehow assumes implicitly some substitution level. It
>>> is
>>> weaker in the sense that it makes the substitution level non constructive
>>> evidence explicit, and does not bound it.
>>>
>>> The UDA is only a "human" way to get quickly the main consequences:
>>> physics
>>> is reduced, by the usual Occam, to arithmetic. And so is testable, and so
>>> "theology" is (again) a science.
>>>
>>> The AUDA is just the "machine" theory.
>>>
>>
>> Yes. My point was just this: assuming CTM is not a fringe idea, it's
>> perhaps even the mainstream nowadays*.
>>
>
> I would say that it might be mainstream since Descartes, but of course in
> an inconistent dualit or materialist context. Diderot defined implicitly
> "rationalism" by "mechanism", but again, without realizing that his belief
> in Matter is "religious", in fact Aristotelian.
> Mechanism is also present in almost all of the indian philosophy,
> including detractors of it, and some school intutited, arguably, for
> immaterialism from it. Of course, Indians have sting materialist schools,
> even "strong atheists" school (arguing against after-life, and some even
> against consciousness, soul, person, etc.).
>
>
>
> I said it in reply to Pierz
>> suggestion that I am assuming something weird or unusual, only known
>> in this mailing list.
>>
>
> OK. No problem :)
>
>
>
>> *Of course many people are not aware of the consequences that you
>> explores with UDA and AUDA.
>>
>
> To say the least.
>
> I took some time to realize that the self-called "free-thinkers" were
> actually the guardian of the Aristotelian materialist dogma.
>
> I took some long time to realize that the average scientists confuse the
> strong evidence that there is a physical reality, with evidence that there
> is a primary physical reality.
>
> To make just one realist dream is enough to doubt and understand that
> "seeing X" is not "proving X", still less knowing X. But I guess people
> prefer to not doubt some X, for reason of thought habit.
>
>
>
>
>
>> I am not sure it is possible to
>>>> discuss this issues while shielding ourselves from theories of mind.
>>>> With MWI all branches exist anyway. Perhaps what we are discussing is
>>>> necessarily about subjective (first person) states.
>>>>
>>>> So you are talking different
>>>>> languages.
>>>>>
>>>>
>>>>
>>>> Not sure I agree. We are perhaps implicitly assuming different theories
>>>> of
>>>> mind.
>>>>
>>>> I don't know if Telmo is aware or not of the conventional view of
>>>>> decoherence - that it is a matter of the spread of information into the
>>>>> environment by means of physical interactions between particles.
>>>>> Telmo's
>>>>> musings about the effect of destroying memory (could it change the
>>>>> measure
>>>>> of different futures?) clearly expresses this subjectivist view.
>>>>>
>>>>
>>>>
>>>> I get your point with decoherence.
>>>> Again, I would say that it all depends on theories of mind. What does
>>>> mind supervene on? Perhaps it is true that every single coupling with
>>>> the environment prevents the current observer state to become
>>>> compatible with other branches. But can we be sure? I feel that such
>>>> certainties come from a strong belief in emergentism (which I cannot
>>>> disprove, but find problematic).
>>>>
>>>
>>>
>>> It is impossible to recohere the past, FAPP.
>>>
>>> But only FAPP. To make the blue T-rex interfereing with the red-T-rex, we
>>> must erase the trace of particle interaction between the T-rex in its
>>> whole
>>> light-cone, and this without forgetting the particles "swallowed" by the
>>> black-holes, etc. It is just completely impossible, but to derive from
>>> that
>>> the unicity of the past, is, it seems to me (and you if I understood
>>> well)
>>> is invalid.
>>>
>>
>> Right, I agree with you and Pierz on this. My point was more on what
>> you address below.
>>
>>
>>>
>>>
>>>
>>>> FWIW, you
>>>>> are expressing my own understanding of the situation: there can be no
>>>>> superposition of red and green screens or dinosaurs, or dead and live
>>>>> cats,
>>>>> because there can be no quantum superposition of macroscopic objects.
>>>>> Superpositions of wave functions are only possible for systems isolated
>>>>> from
>>>>> interaction with their environment, which is why quantum computers are
>>>>> so
>>>>> fricking hard to make: keeping aggregates of particles isolated from
>>>>> interactions with the surrounding environment is exponentially more
>>>>> difficult as the system grows in size.
>>>>>
>>>>
>>>>
>>>> The main question for me is this: can two branches hold different
>>>> observer states, if they differ only by things that are not
>>>> observable?
>>>>
>>>
>>>
>>> I would say no, intuitively. I would even say "no" just for the things
>>> not
>>> observed, even when observable. But this has to be tempered by the fact
>>> that
>>> any interaction will count as an observation, making super-exponentially
>>> hard to indeed recover a macroscopic superposition in the past, even the
>>> very close past.
>>>
>>
>> What if the substitution level turns out to be at a higher level than
>> quantum? E.g. at the level of the neurons and their connections and
>> activations levels?
>>
>
> That would enlarge the uncertainty spectrum on the realities we can access
> without losing anything subjective.
A point against, I assume.
> It would help the doctor to build the artificial brain.
A point in favour.
> It could also make more difficult to justify the smallness of Planck
> constant, and to explain why the quantum seems more obviously present in
> the micro-states,
Against?
> Decoherence would be easier to fight against,
OK
> and quantum computing would be more easy to be realized.
How, if the substitution is above the quantum boundary?
> This
>
> makes me think that the quantum level is boundary of the substitution
> level.
I don't follow all of the above. Do you mean a boundary above which, or
below which, a plausible substitution might be made?
David
>
>
>
>
>> Of course, that might change the day we succeed in building
>>> a fault tolerant (topological perhaps) quantum computer.
>>>
>>
>> Why?
>>
>
> It seems to me that the explanation is what I said below
>
>
>
>> ... if a T-rex made a solid topological quantum qubit,
>>> in the state 0+1, we would have a past with 0, and a past with 1, as
>>> long as
>>> we don't look at it.
>>>
>>
>
> So, in that case, we have a multiple past, and by observing the T-rex
> qubits, in the {0,1} base, we would "determine" it. But we can also not
> measuring it, and observe some interferences justifying that the qubit did
> not decohere.
>
> Bruno
>
>
>
>
> I read, already a long time ago, some experimental
>>> evidence of temporal Bell's inequality going in this direction, and I
>>> think
>>> we don't even need to test them, as we get them with the usual Bell's
>>> inequality violation, if we accept special relativity (and some amount of
>>> physical realism (not the full materialism, to be sure).
>>>
>>> Bruno
>>>
>>>
>>>
>>>
>>>
>>>> Telmo.
>>>>
>>>>
>>>>>>
>>>>>> Bruce
>>>>>>
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>>>
>>>
>>> http://iridia.ulb.ac.be/~marchal/
>>>
>>>
>>>
>>>
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