On Thu, Nov 14, 2019 at 10:58 PM Bruno Marchal <[email protected]> wrote:
> On 11 Nov 2019, at 12:35, Bruce Kellett <[email protected]> wrote: > > On Mon, Nov 11, 2019 at 8:37 PM Bruno Marchal <[email protected]> wrote: > > On 10 Nov 2019, at 20:01, Alan Grayson <[email protected]> wrote: >> > > >> On Sunday, November 10, 2019 at 5:42:50 AM UTC-7, Bruno Marchal wrote: >> >> Once the cat is alive + dead, he remains in that state for ever. >>> >> >> *Then how come we NEVER observe that state? AG* >> >> >> Because the observable are defined by their possible definite outcome, >> and for reason already explained, macroscopic superposition decoder, that >> is get entangled with the environment at a very high speed. So, if you look >> at the cat in the a+d state, you are duplicate almost immediately into a >> guy seeing the cat alive + the guy seeing the cat dead, and QM explained >> why they cannot interact, although they might interfere themselves. >> > > That is exactly a preferred basis -- which you seem to want to deny. > > > I have never denied a preferred basis, as preferred by the evolution of > the type of observer we are (like molecular biological organism, where > position plays an important role). > As has been pointed out, evolution of observers plays no role in the existence of a preferred basis. The preferred basis arises from the normal physical interactions of quantum states with the environment. Observers play no role in this process. That is the message of Everett -- we must eliminate any mention of observers (or measurement) from our account of physics. > What I deny is that the MWI implies that some base are more important in > physics than other. > That is where you are 100% wrong. The preferred basis, its existence and development, is central to physics. Sure, we can describe Hilbert space in any basis whatsoever, but we do not perceive Hilbert space -- the world we perceive definitely has a preferred basis. > The universal wave function can be described in any base, but the internal > observer will “choose” the base corresponding to their most useful sensory > apparatus. > No, again, it is not a matter of personal choice. The preferred basis is determined by the basic dynamics of the physical world, independently of any observer, or any observer's choice. > It is a bit like a planet and life: there are “preferred planet” having > the right conditions for life to develop. Similarly, consciousness can only > differentiate in the base in which Turing universal machine can also > differentiate. > It is not at all like the fact that only certain planets have the right conditions for life. Life is irrelevant to the preferred basis. The important concept, as Zurek has stressed in his development of Quantum Darwinism, is the emergence of a classical world from the quantum substrate. Central to this, is the possibility of the formation, in the environment, of many copies of the information concerning the outcome of a quantum process. These many copies are central to the possibility of many observers coming to see the same result, and that leads to the emergence of an objective classical world. It is this objective classical world that is the basis of our experience, and it is that world that we are required to explain by our physics. Given that we have access only to a limited subset of the total information, we definitely have a mixed state -- this is the origin (in quantum Darwinism) of quantum jumps. Zurek's insight here is profound. In order for the basis to be irrelevant, we would have to have access to all the copies of the information. If we have such access, then objectivity is lost -- others cannot access the information without disturbing the system. Consequently, independence of basis entails solipsism -- where only one individual would control all the information, and he can order this in any basis he likes. But that is not how things are in practice. 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 [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/everything-list/CAFxXSLT54Ecm3VfqJi5-Abn_h4cg%2BuFBGSdWgymHSG8b01MuVg%40mail.gmail.com.
