On Monday, October 15, 2018 at 3:28:17 PM UTC, agrays...@gmail.com wrote: > > > > On Monday, October 15, 2018 at 11:17:56 AM UTC, Bruce wrote: >> >> From: <agrays...@gmail.com> >> >> >> On Sunday, October 14, 2018 at 5:08:42 PM UTC, smitra wrote: >>> >>> On 14-10-2018 15:24, agrays...@gmail.com wrote: >>> > In a two state system, such as a qubit, what forces the interpretation >>> > that the system is in both states simultaneously before measurement, >>> > versus the interpretation that we just don't what state it's in before >>> > measurement? Is the latter interpretation equivalent to Einstein >>> > Realism? And if so, is this the interpretation allegedly falsified by >>> > Bell experiments? AG >>> >>> It is indeed inconsistent with QM itself as Bell has shown. Experiments >>> have later demonstrated that the Bell inequalities are violated in >>> precisely the way predicted by QM. This then rules out local hidden >>> variables, therefore the information about the outcome of a measurement >>> is not already present locally in the environment. >>> >>> Saibal >>> >> >> What puzzles me is this; why would the Founders assume that a system in a >> superposition is in all component states simultaneously -- contradicting >> the intuitive appeal of Einstein realism -- when that assumption is not >> used in calculating probabilities (since the component states are >> orthogonal)? AG >> >> >> I think the problem arises with thinking of a superposition as an >> expression of a fact of the system being in all components of the >> superposition simultaneously. >> > > *This is precisely what I argued here as recently as last summer, > whereupon those who claim knowledge of quantum computers asserted that > qbits assume exactly that, that qbits are in both states simultaneously. AG* > > This mistaken interpretation leads to the Schrödinger cat paradox, which >> you have worried about for a while. >> >> But this is a mistake. A superposition is just an expansion of a wave >> function in some basis or the other -- the choice of basis is arbitrary, so >> it makes no sense to think of this expansion as representing anything that >> happens in "reality" (in Einstein's sense of "reality"). >> > > *I agree and argued the same last summer. I quoted Dirac, which quote > appears in the Wiki article on quantum superposition, who makes the mistake > you reference, which IMO Schroedinger falsified. Some claim Schroedinger > didn't falsify the error (show it was an error) because he was unaware of > decoherence. I disagree with this analysis. AG* > > The state is still the original state until decoherence kicks in and then, >> because of einselection of a preferred basis, we can say that the separate >> states are "real" -- namely orthogonal, so that one other other is chosen. >> Until that time, the only state around is the original state, as can be >> demonstrated by the possibility of recoherence, in which case you recover >> just the initial state and nothing else. >> > > *Aren't the component states orthogonal prior to decoherence? IIUC, they > must be if they have distinct eigenvalues. AG* >
*I conclude that not every superposition has components that are eigenvectors of the operator for the observable. So these components are not orthogonal. But there is always an expansion whose components are eigenvectors and thus are orthogonal. I don't think this has anything to do with decoherence. AG* *What continues to puzzle me is why the alleged experts here of quantum computing (and I think Wiki as well) claim that qbits are in both states simultaneously, when we know this is not a correct interpretation of a superposition. Does the theory of quantum computing depend in any way on what appears to be an erroneous interpretation of a superposition? TIA, AG* > >> So for Schrödinger's cat, for example, if you could recohere the system >> after one hour, say, you would find the cat alive in the box and the vial >> of cyanide unbroken with the radioactive atom undecayed -- exactly as you >> set the system up. It is only because the cat and apparatus are large warm >> classical objects that this recoherence is not possible FAPP. To think of >> the cat at some intermediate time as being both dead and alive is just a >> confusion -- it is at all times either one or the other. >> >> 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.
