On Tuesday, August 14, 2018 at 1:20:26 AM UTC, Bruce wrote: > > From: Jason Resch <jason...@gmail.com <javascript:>> > > On Mon, Aug 13, 2018 at 12:05 AM Bruce Kellett <bhke...@optusnet.com.au > <javascript:>> wrote: > >> From: Jason Resch <jason...@gmail.com <javascript:>> >> >> >> On Sun, Aug 12, 2018 at 5:06 AM Bruno Marchal <mar...@ulb.ac.be >> <javascript:>> wrote: >> >>> >>> On 11 Aug 2018, at 02:29, Bruce Kellett <bhke...@optusnet.com.au >>> <javascript:>> wrote: >>> >>> They do not "belong to different branches" because they do not exist, >>> and have never existed. This notion seems to be important to your idea, and >>> I can assure you that you are wrong about this. >>> >>> >>> How could that be possible? You suppress the infinities of Alice and Bob >>> only because you know in advance what is the direction in which Alice will >>> make her measurement. What if she changes her mind? >>> >>> >> Right. >> >> I would like Bruce to consider the case Alice measures alternately x and >> z spin axes of an electron 1000 times and interprets those measurement >> results as binary digits following a decimal point to define the real >> number to which she will set her measurement angle to (before she measures >> her entangled particle). >> >> Certainly in the no-collapse case there would be at least 2^1000 Alices >> who perform the measurement at each of the possible measurement angles that >> can be defined by 1000 binary digits. What I wonder is how many Alices >> Bruce would believe to exist in this scenario before she measures her >> entangled particle. >> >> >> How do 2^1000 copies of Alice make any difference? Each measures the >> entangled particles only once. Besides, This is not what is done. I see >> little point in making up alternative scenarios -- why not explain the >> straightforward original scenario? Imaginary copies are beside the point. >> >> If you cannot focus your attention on the original scenario, I see little >> point in your trying to do physics. >> > > I bring this question up because you repeatedly refer to only "one Alice" > before the measurement, and also say that Alice and Bob are "in one and the > same branch" prior to measurement. But normal QM without collapse would > say Alice and Bob are branching all the time, even before they measure > their entangled pair. So isn't it necessary to take this into > consideration (that this is implicitly the original scenario): > > > You seem to be trying to re-introduce the 'jellification' or 'mushiness' > that so worried Schrödinger. Fortunately, that worry has long since been > laid to rest by the advent of modern decoherence theory. In that theory, > splitting of the world into distinct (quasi-)classical branches occurs only > when the microscopic quantum phenomenon has been amplified to macroscopic > level, and a thermodynamically irreversible record (or many records, as > suggested by Zurek) has been laid down in the environment. So micro-level > quantum events generally do not lead to splittings into disjoint worlds, > and we don't need to worry about the fact that a genuine classical world > emerges from the quantum substrate. > > So there are no 'many Alices and Bobs' before or during the experiment -- > there is only one classical Alice and one classical Bob who get involved in > the experiment. Besides, even if, by chance, some quantum event in Alice's > makeup does get amplified, so that copies of Alice exist in superposition, > that makes no essential difference. In the normal way with quantum > superpositions, we simply select out one typical Alice-Bob pair and work > with these. So my implicit assumption of just one Alice-Bob pair is > completely harmless. If you want to claim that quantum jellification makes > a difference, then it is up to you do make the case -- which no one has > seriously attempted to do, for very good reason. > > There are many Alices, and many Bobs, and depending on the experimental > setup, many measurement angle choices? > > > No, there are not, and even if there were it would make no difference. > Alice and Bob have to measure the same entangled pair and persist as > identifiable individuals for long enough to record their results and later > compare them -- or else they would not observe any correlations at all! The > entangled singlet does not change its identity in its passage between Alice > and Bob -- it has to maintain its coherence, or else it is not en entangled > pair. So the Bob that measures the partner of Alice's particle is really > and truly the same Bob that she met for breakfast before the experiment > began. > Your (and Bruno's) idea that somehow their identities are not fixed > because of quantum fluctuations is truly fatuous. >
*Jason isn't thinking of quantum fluctuations. Rather, he's thinking of all possible orientations of the SG device, and extending the principle, in my view erroneously, that all possible results of spin, is intended to mean the possible results of all possible experiments which depend on orientation. AG * > > 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.
