> On 11 Jun 2018, at 12:59, [email protected] wrote: > > > > On Monday, June 11, 2018 at 10:40:13 AM UTC, Bruno Marchal wrote: > >> On 11 Jun 2018, at 07:06, [email protected] <javascript:> wrote: >> >> >> >> On Monday, June 11, 2018 at 2:20:47 AM UTC, [email protected] >> <http://gmail.com/> wrote: >> >> >> On Monday, June 11, 2018 at 2:09:25 AM UTC, Bruce wrote: >> From: <[email protected] <>> >>> On Monday, June 11, 2018 at 1:37:53 AM UTC, Bruce wrote: >>> From: Bruno Marchal <[email protected] <> >>> Everett prove the contrary, and he convinced me when I read it. I found >>> “his proof” used in many books on quantum computing, although with >>> different motivation. Thee result of an experiment, obviously depend of >>> what you measure, but when you embed the observer in the wave, you get that >>> what they find is independent of the choice of the base used to describe >>> the “observer” and the “observed”. If not, the MW would already be refuted. >>> >>> In that case, MW is refuted. Clearly, what the observer finds is dependent >>> on the basis in which he is described. Or else experiments would not have >>> definite results when described in the laboratory from the 1p perspective. >>> Even if you take the 'bird' view of the whole multiverse -- which is, I >>> agree, independent of the basis in which it is described -- the view of any >>> observer embedded in the multiverse is totally basis-dependent. That is, >>> after all, what we mean by 'worlds' -- the view from within, or the 1p >>> view. But that view depends on how you describe it: the way in which you >>> partition the multiverse itself. Only certain very special bases are robust >>> against environmental decoherence -- how else do you resolve the >>> Schrödinger cat issue? >>> >>> Bruce >>> >>> So you find the resolution in the fact that according to decoherence >>> theory, the cat is simultaneously alive and dead for only short time? AG >> >> Decoherence has resolved the basis question long before the cyanide has hit >> the cat. >> >> Bruce >> >> I don't think you've answered the question. Isn't the cat in a superposition >> of alive and dead before the cyanide hits? Did Schroedinger write an >> incorrect wf? If so, what is the correct one IYO? AG >> >> I surmise your position is that decoherence happens so quickly, that the >> superposition Schroedinger wrote was really a mixed state. If so, I don't >> see this as a solution to the paradox, unless you want to allow the >> existence of a simultaneously alive and dead cat for a very, very short >> time. AG > > > That is why I prefer Bohm’s version of the cat, where the cat alive/dead > state is corrupted with the up/down state of some particles. It ease the mind > by showing that the time is not an issue. If you can completely isolate the > cat from the environment (which is technically impossible), you can maintain > the cat in the dead + alive superposition state as long as you want. If you > isolate successfully the entire laboratory including you, Then, someone else > can resurrect the cat, relatively to himself, despite you saw it dead. > > The reason why we cannot do this in principle, is that we cannot isolate the > cat, and if the cat, when the cat is dead+alive, interact with some particles > in the environment, you can no mare factorize the cat state, without tracking > that particles. > > I don’t think it make sense to confine the superposition in the microscopic > domain, nor in the short-time domain. If the SWE is correct, the > superposition never disappear, unless a collapse assumption is made, but then > it cannot be described by QM. Only by QM + exception rules for the observer > or the measuring apparatus, but there are no evidences for that. > > Bruno > > See my solution to the S Cat on the other thread. Since the cat can never be > isolated, it can never be in a superposition, which generates the paradox. > And since coherence can never occur, no need to apply decoherence! AG
I am not sure this make sense (with the SWE). The cat is always isolated, in some sense. Let me prepare an electron in the state (u + d) (the superposition of up + down, I will not use Dirac notation, because it is not easy in mail). Then I put the cat near a device which kill it if the electron is down, and let him alive if the spin is up. What happens is this. In between the cat and me there are particles, some bouncing on the cat and other, soon or later bounding on some particles having bounce with the cat, or with a particles having bounced … etc. Let us simplify, and consider that there is only one such particles, and it goes in the state - if the cat is dead, and in the state + if the cat is alive. The cat is describe by C, and C°° described the cat alive, and C° describes the cat dead. We have the overall state (in the box if you want) C(u+d) By linearity of the tensor product (used here to describe a multi-body system), that is the same as the state (Cu + Cd) But the cat looked at the spin of my electron, so the state evolved toward (C°° u + C° d), OK? If all this is in the box, and the box is truly isolated from me (and thus from all molecules I could interact with), I could in principle measure that system in some different base, in the Hilbert space spanned in base involving the cat state and the electron state and get the interferences, so no reduction collapse occurred. But now there is that particle P, between me and the cat, which I am not aware of. When P bounces on the cat, it becomes P°° if the cat is alive, and P° if the cat is dead. The state of the cat + that particles (and my electron) is (P°° C°° u + P° C° d) Now, I would be aware of that particles, and able to measure it, I could still build an apparatus (in principle) and find the interference. I can transform P°° + P° into some “amnesic” P, and factor it from (P°° C°° u + P° C° d) = P(C°° u + C° d). It is a so-called quantum erasing. But I am not aware of that particles, (nor of the trillions one around, and I cannot measure it), so, I cannot bring P°° + P° to some P, so as to factor it from (P°° C°° u + P° C° d) and get P(C°° u + C° d), and test the interference for the factor involving the cat superposition. But what happens is that even if the cat is not isolated at all, with trillions of particles in between me and the cat, the superposition of the cat is only contaminating those particles, locally, until all my body is itself duplicated (multiplied). Note that (C°° u + C° d) is a singlet state. It means that the cat state is correlated to the spin state, and this for all directions, not just those determine by u and d. That is helpful to resurrect the cat, if by chance we succeed in tracking the many particles in between. Even not isolated at all, the dead + alive cat remains in that state forever, well until the cat died normally, which will happen in the normal world. From the cat points of view it/he/she remains alive in some branch. This reasoning can be done in a different base. The global multiverse will look different, but the relative states of the cat, and its relative probabilities will be the same, for the corresponding possible measurements. That is basically what Everett proves page 38 in the book edited by Graham and deWitt(*). Bruno (*) https://www.amazon.com/Interpretation-Quantum-Mechanics-Princeton-Library/dp/069161895X > > > -- > 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 [email protected] > <mailto:[email protected]>. > To post to this group, send email to [email protected] > <mailto:[email protected]>. > Visit this group at https://groups.google.com/group/everything-list > <https://groups.google.com/group/everything-list>. > For more options, visit https://groups.google.com/d/optout > <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 [email protected]. To post to this group, send email to [email protected]. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
