> On 1 Aug 2018, at 02:11, Brent Meeker <[email protected]> wrote: > > > > On 7/31/2018 2:43 PM, [email protected] <mailto:[email protected]> > wrote: >> >> >> On Tuesday, July 31, 2018 at 7:14:53 PM UTC, Brent wrote: >> >> >> On 7/31/2018 6:43 AM, [email protected] <javascript:> wrote: >> >> >> On Tuesday, July 31, 2018 at 6:11:18 AM UTC, Brent wrote: >> >> >> On 7/30/2018 9:21 PM, [email protected] <> wrote: >> >> >> On Tuesday, July 31, 2018 at 1:34:58 AM UTC, Brent wrote: >> >> >> On 7/30/2018 4:40 PM, [email protected] <> wrote: >> >> >> On Monday, July 30, 2018 at 7:50:47 PM UTC, Brent wrote: >> >> >> On 7/30/2018 8:02 AM, Bruno Marchal wrote: >> and claims the system being measured is physically in all eigenstates >> simultaneously before measurement. >> >> >> Nobody claims that this is true. But most of us would I think agree that >> this is what happens if you describe the couple “observer particle” by QM, >> i.e by the quantum wave. It is a consequence of elementary quantum mechanics >> (unless of course you add the unintelligible collapse of the wave, which for >> me just means that QM is false). >> >> This talk of "being in eigenstates" is confused. An eigenstate is relative >> to some operator. The system can be in an eigenstate of an operator. Ideal >> measurements are projection operators that leave the system in an eigenstate >> of that operator. But ideal measurements are rare in QM. All the >> measurements you're discussing in Young's slit examples are destructive >> measurements. You can consider, as a mathematical convenience, using a >> complete set of commuting operators to define a set of eigenstates that will >> provide a basis...but remember that it's just mathematics, a certain choice >> of basis. The system is always in just one state and the mathematics says >> there is some operator for which that is the eigenstate. But in general we >> don't know what that operator is and we have no way of physically >> implementing it. >> >> Brent >> >> I can only speak for myself, but when I write that a system in a >> superposition of states is in all component states simultaneously, I am >> assuming the existence of an operator with eigenstates that form a complete >> set and basis, that the wf is written as a sum using this basis, and that >> this representation corresponds to the state of the system before >> measurement. >> >> In general you need a set of operators to have the eigenstates form a >> complete basis...but OK. >> >> I am also assuming that the interpretation of a quantum superposition is >> that before measurement, the system is in all eigenstates simultaneously, >> one of which represents the system after measurement. I do allow for >> situations where we write a superposition as a >> sum of eigenstates even if we don't know what the operator is, such as >> the Up + Dn state of a spin particle. In the case of the cat, using the >> hypothesis of superposition I argue against, we have two eigenstates, which >> if "occupied" by the system simultaneously, implies the cat is alive and >> dead simultaneously. AG >> >> Yes, you can write down the math for that. But to realize that physically >> would require that the cat be perfectly isolated and not even radiate IR >> photons (c.f. C60 Bucky ball experiment). So it is in fact impossible to >> realize (which is why Schroedinger considered if absurd). >> >> CMIIAW, but as I have argued, in decoherence theory it is assumed the cat is >> initially isolated and decoheres in a fraction of a nano second. So, IMO, >> the problem with the interpretation of superposition remains. >> >> Why is that problematic? You must realize that the cat dying takes at least >> several seconds, very long compared to decoherence times. So the cat is >> always in a classical state between |alive> and |dead>. These are never in >> superposition. >> >> >> When you start your analysis /experiment using decoherence theory, don't you >> assume the cat is isolated from the environment? It must be if you say it >> later decoheres (even if later is only a nano second). Why is this not a >> problem if, as you say, it is impossible to isolate the cat? AG >> >> That it is impossible to isolate the cat is the source of the >> absurdity...not that it exists in a superposition later. >> >> But if you claim the cat decoheres in some exceedingly short time based on >> decoherence theory and the wf you write, taking into account the apparatus, >> observer, and remaining environment, mustn't the cat be initially isolated >> for this to make sense? AG > > It never made sense. That it didn't make sense was Schroedinger's point, he > just didn't correctly identify where it first failed to make sense, i.e. in > the idea that a cat could be isolated. Since the cat can't be isolated then } > |alive> and |dead> can only appear in a mixture, not in a coherent > superposition.
But a mixture is only a relative notion. It is the superposition as seen from inside each superposition. In the universal wave, no mixture ever appear (with Everett theory). Bruno > > Brent > > >> >> It doesn't go away because the decoherence time is exceedingly short. >> >> Yes is does go away. Even light can't travel the length of a cat in a >> nano-second. >> >> And for this reason I still conclude that Schroedinger correctly pointed out >> the fallacy in the standard interpretation of superposition; namely, that >> the system represented by a superposition, is in all components states >> simultaneously. AG >> >> It's not a fallacy. It just doesn't apply to the cat or other macroscopic >> objects, with rare laboratory exceptions. >> >> Other than slit experiments where superposition can be interpreted as the >> system being in both component states simultaneously, why is this >> interpretation extendable to all isolated quantum systems? AG >> >> ?? Any system can be mathematically represented as being in a superposition >> of different basis states. It's just a consequence of being a vector in a >> vector space. Any vector can be written as a sum of other vectors. >> >> OK, never had a problem with this. AG >> >> Your use of the words "interpreted" and "this interpretation" is unclear. >> >> I am using those words as I think Schroedinger did, where he assumes a >> system in a superposition of states, is in all component states >> simultaneously. It is from that assumption, or interpretation, that he finds >> the contradiction or absurdity of a cat alive and dead simultaneously. AG >> >> >> Any old plane polarized photon can be represented as being in a >> superposition of left and right circular polarization. It is not the case >> that a system is in all basis states at once unless you count being in state >> |x> with zero amplitude as being in x. >> >> Brent >> >> >> >> 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. > 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. 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. For more options, visit https://groups.google.com/d/optout.
