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 said it in reply to Pierz suggestion that I am assuming something weird or unusual, only known in this mailing list. *Of course many people are not aware of the consequences that you explores with UDA and AUDA. >> 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? > Of course, that might change the day we succeed in building > a fault tolerant (topological perhaps) quantum computer. Why? > Unfortunately, the > T-rex missed them. yet, 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. 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 >>>> >>> -- >>> You received this message because you are subscribed to the Google Groups >>> "Everything List" group. >>> To unsubscribe from this group and stop receiving emails from it, send an >>> email to everything-list+unsubscr...@googlegroups.com. >>> To post to this group, send email to everything-list@googlegroups.com. >>> Visit this group at https://groups.google.com/group/everything-list. >>> For more options, visit https://groups.google.com/d/optout. >> >> >> -- >> You received this message because you are subscribed to the Google Groups >> "Everything List" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to everything-list+unsubscr...@googlegroups.com. >> To post to this group, send email to everything-list@googlegroups.com. >> Visit this group at https://groups.google.com/group/everything-list. >> For more options, visit https://groups.google.com/d/optout. > > > http://iridia.ulb.ac.be/~marchal/ > > > > > -- > You received this message because you are subscribed to the Google Groups > "Everything List" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to everything-list+unsubscr...@googlegroups.com. > To post to this group, send email to everything-list@googlegroups.com. > Visit this group at https://groups.google.com/group/everything-list. > For more options, visit https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups "Everything List" group. 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