> On 18 Jul 2018, at 05:02, [email protected] wrote: > > > > On Wednesday, July 18, 2018 at 2:00:47 AM UTC, [email protected] wrote: > > On Tuesday, July 17, 2018 at 12:00:08 PM UTC, Bruno Marchal wrote: > >> On 16 Jul 2018, at 23:08, [email protected] <> wrote: >> >> >> >> On Monday, July 16, 2018 at 8:30:58 AM UTC-6, Bruno Marchal wrote: >> >>> On 13 Jul 2018, at 01:55, [email protected] <> wrote: >>> >>> >>> >>> On Wednesday, July 11, 2018 at 2:16:24 PM UTC-6, [email protected] >>> <http://gmail.com/> wrote: >>> >>> >>> On Tuesday, July 10, 2018 at 4:42:44 PM UTC-6, Brent wrote: >>> >>> >>> On 7/10/2018 3:01 PM, [email protected] <> wrote: >>>> IIRC, the above quote is also in the Wiki article. It's not a coherent >>>> argument; not even an argument but an ASSERTION. Let's raise the level of >>>> discourse. It says we always get a or b, no intermediate result when the >>>> system is in a superposition of states A and B.. Nothing new here. Key >>>> question: why does this imply the system is in states A and B >>>> SIMULTANEOUSLY before the measurement? AG >>> >>> Because, in theory and in some cases in practice, there is a direct >>> measurement of the superposition state, call it C, such that you can >>> directly measure C and always get c, but when you have measured and >>> confirmed the system is in state c and then you measure A/B you get a or b >>> at random. The easiest example is SG measurements of sliver atom spin >>> orientation where spin UP can be measured left/right and get a LEFT or a >>> RIGHT at random, but it can be measured up/down and you always get UP. Any >>> particular orientation can be written as a superposition of two orthogonal >>> states. >>> >>> When you're trying to explain esoteric issues to a moron in physics, you >>> need to be more explicit. These are the issues that cause confusion and >>> caused me to fail to "get it". After some subsequent posts, you seem to be >>> saying that in an SG spin experiment where the measurement base is UP/DN, >>> the system being measured is ALSO in a superposed LEFT/RIGHT state which is >>> also measured (by an SG device designed to measure spin?), and that the >>> LEFT/RIGHT superposed state persists with some persistent eigenvalue after >>> UP/DN is measured. It's murky for us morons. How does one get the system >>> to be measured in a superposition of RIGHT/LEFT; what is the operator for >>> which that superposition is an eigenstate, and what is the value of the >>> persistent eigenvalue? >>> >>> Furthermore, you finally assert that since the RIGHT/LEFT state persists -- >>> meaning that particle is in some DEFINITE state after the spin is measured >>> -- and since (as you finally, finally assert) that that state can be >>> written as a superposition of UP/DN, all is well -- in the sense that we >>> can now be certain that the system is physically and simultaneously in the >>> UP and DN states (which I am claiming is a fallacy). >>> >>> HOWEVER, assuming that I understand your argument after filing the gaps in >>> your presentation (and pointing to some unanswered issues), I now must >>> "rant" again that the UP/DN superposed representation is NOT unique. Thus, >>> since there are finitely many or uncountable many such representations, and >>> since (as per LC) QM has no preferred basis, your argument for the physical >>> simultaneity of UP and DN states fails. I mean, I could write the >>> superposed states in the basis (UP + DN) and (UP - DN), or in many other >>> bases. Absent uniqueness of bases, one cannot assert that the system is >>> physically and simultaneously in any particular pair of basis vectors. >>> >>> AG >>> >>> I've been looking over your references to Peres. CMIIAW, but AFAICT he >>> doesn't deal with the issue I have been "ranting" about; namely, the >>> non-uniqueness of bases, implying IMO that the concept of simultaneous >>> physical states of the components of a superposition is an additional, >>> unsupported assumption of QM which leads to some popular misconceptions of >>> what QM is telling us. >> >> >> Then you need to find a new explanation of the interference that occurs in >> basically all quantum experiments, like the two slits, the statistics of >> results with Stern-Gerlach spin measuring apparatus, etc. >> >> I am not trying to explain the interference. > > You should. That is the whole problem. How can we get interference if the > wave describes only our knowledge state. The reason why we consider the wave > physically real is that the wave interfere, even the wave associate to a > single particle. > > > >> Rather I am pointing out an unnecessary assumption that leads to paradoxes. > > ? > > > > >> See comment below. AG >> >> The whole point of the physical wave amplitudes is that the diverse >> superposed components have a physical role, through destructive or >> constructive, or in between, interference. >> >> The amplitudes give probabilities of occurrence, confirmed by measurements. >> Nothing more. You forget that the components of the superposition are >> usually assumed to be orthogonal states, which don't mutually interfere. >> Thus, you are claiming to explain interference from component states which >> don't interfere. > > That is what we do with any wave, and there is no problem there. It just that > cos(pi/2) is zero. > > You're mistaken. In quantum superpositions, orthogonal does not mean 90 deg > out of phase -- as is the case for ordinary vectors in the plane -- but that > the inner product is zero.
That is what I mean. > Hence, since the inner product of all components of a superposition are > mutually orthogonal, or zero, how can you claim that interference exists? AG A position (say at one hole) is models by a vector in an abstract linear space. The position at the other hole (I’m thinking of the two slit experiences) is represented by another vector. The fact that the two position are distinct and distinguishable made them described by orthogonal vector in that abstract linear space (an Hilbert space). The interference of statistics comes from the fact that the available stories are described by a wave function, which describe my relative ignorance on which histories I belong to. When the to holes are open, the particle state might be described by a superposition of those two position, which makes some angle different from PI/2, so that interference terms can appear, and indeed can be reflected on the screen by interference fringes if I repeat the experience with the same wave again and again. > > The problem here is that the amplitude of the wave, when squared, give a > probability to find a particle somewhere, but this forced us to make the wave > physical, as it will behave differently if there is two slits, one splits, > etc. > > > > > >> Try this; in the case of radioactive decay, can you define the interference >> between Decayed and Undecayed states? AG > > It is not relevant. I prefer ro use superposition of spin, than a temporal > phenomenon. > > OK, then use superposition of spin and describe the interference. Note that > since the Up and Dn are orthogonal, there is no interference. The interferences are between waves, not state. With the spin Up can be written as superpositions, like Up = 1/sqrt(2) Up’ + 1/sqrt(2) Down Down = 1/sqrt(2) Up’ - 1/sqrt(2) Down The interference comes from sum and difference of such superpositions. Take the two “orthogonal” slits: in classical physics you can add up and multiply he probabilities in the usual way for the alternatives and sequence of events, but in quantum mechanics, you have an amplitude, which describes a “wave of history”, and to predict the final state, you need to square the amplitude, and this takes into account all path, basically because (a+ b)^2 is different from a^2 + b^2. > That is, generally, when we write a superposition where the components are > eigenstates, it is assumed the components are mutually orthogonal, hence no > interference. AG >> >> Note that the discussion here supposed the quantum theory, but you are free >> of course to propose an alternative. Many have tried without success, though. >> >> What I am doing is asking the usual suspects the basis for the assumption >> that the components of a superposition physically exist simultaneously. So >> far, IMO, their silence is pregnant. They can't. AG > > > Then explain me what happens in the two slit experiments, when we send the > particles “one by one”. > You need superposition to explain this. It is the base of QM: particles > dynamics are described by waves, and those wave do superpose and interfere, > even when the particles are alone. > > I don't have to explain everything, and in fact I cannot. All I want to know > is how can there be interference among components of a superposition, when > they are mutually orthogonal. AG I don’t really understand the language. You have interference when the wave of a particle describe different outcomes possible for some observable. If it is the position, like in the two slits, interference comes from the existence of state “superposing” two (or more) states from the base. The interference is, somehow, the superposition itself, when recombined at some place (screen, interferometer, etc.) Do you know the book by David Albert “Quantum Mechanics and Experience”, it is quite good pedagogically, and he explains well the “problem”. He dmisloh Everett very badly (good for Everett!), and defend Bohm quite unconvincingly (for me at least). But he introduces very well the basic core theory, using only very elementary algebra. Bruno > > > Bruno > > > > > >> >> Bruno >> >> >> >> >> >>> Incidentally, when you earlier referred to a RIGHT/LEFT superposition, did >>> you mean circular polarization, or right and left directions in a SG >>> apparatus in relation to Up/Dn measurements? TIA, AG >>> >>> This is true in general. Any state can be written as a superposition of >>> states in some other basis. But it is not generally true that we can >>> prepare or directly measure a system in any given state. So those states >>> we can't directly access, we tend to think of them as existing only as >>> superpositions of states we can prepare. >>> >>> Brent >>> >>> -- >>> 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 >>> <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 >> <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] > <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. 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