On Thursday, October 18, 2018 at 8:33:10 PM UTC, Brent wrote: > > > > On 10/18/2018 12:16 PM, agrays...@gmail.com <javascript:> 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 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"). The state is still >> the original state until decoherence kicks in >> > > > *Here's where I think you're mistaken. When the box is closed in the Cat > experiment, time continues to increase, so the wf evolves independent of > decoherence; before it sets in; before it takes effect, however short that > duration might be. But since the expansion of the superposition is > arbitrary wrt the basis used in the expansion, it still makes no sense to > attribute any physical reality to it, much less a simultaneous state of all > components. Do agree with this? TIA, AG * > > > This example gets confused. Schroedinger intended it to be absurd and it > was absurd not only because the cat was both alive and dead at the same > time but also because it suddenly changed to one or the other when he > looked in. In fact there can be non "wf evolves independent of coherence" > when the box is closed. >
*Assuming no decoherence, the wf must evolve while the box is shut since the probability amplitudes are time dependent. AG * > The cat, the box, the very spacetime field of the radioactive decay > products are enough for decoherence to have occurred. The over > idealization makes it hard to discuss these because all talk of the cat in > a superposition is metaphorical. It would be much clearer if you just > discussed a single radioactive atom, say a beta emitter, in a "box" that is > just a location you can inspect in the vacuum. Until you test it the atom > is in a superposition of decayed and not-decayed. Whenever it decays, that > is a definite event; the state of the datom decoheres into mixture of > decayed or not-decayed because of interaction with the degrees of freedom > of the electron and anti-neutrino fields. So the superposition is best > thought of as your mathematical representation of the atom, which changes > when you test it. > *I'll get back to this later. AG* > > I've assumed that your test is just for decayed vs not-decayed. But you > could also consider the direction of emission by looking at the recoil of > the atom. In that case your not-decayed state is a superposition of all > possible recoil directions you can measure and the decayed state > corresponds with just one of those directions. > > > >> 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. >> > > *I can see how recoherence is impossible FAPP, but after some time elapses > the state of the cat could Dead or Alive; not necessarily the original > state, Alive. A*G > > > When recoherence is no longer possible that's a real physical change. The > system has evolved. > > Brent > > >> 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. >> > > *The Cat does have an intermediate state since time is evolving causing > the wf to evolve, but as I argue above, it's not in both states of the > superposition because the choice of basis is arbitrary, and by extension, > certainly not in both states simultaneously. I generally agree with your > arguments, which I articulated half-a-dozen times or more last summer, but > no one here seemed to understand or agree. When you remind us that the > choice of basis is arbitrary, this is KEY, and all one has to do is apply > what's anathema to see the seminal error; common sense applied to the fact > that the basis used in the superposition is arbitrary! It seems there > remains an undeserved impulse, a cottage industry as it were, to claim some > mysteries in QM that don't exist. 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-li...@googlegroups.com <javascript:>. > To post to this group, send email to everyth...@googlegroups.com > <javascript:>. > 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.
