> On 1 Aug 2018, at 20:52, Brent Meeker <[email protected]> wrote: > > > > On 8/1/2018 4:07 AM, Bruno Marchal wrote: >> >>> On 1 Aug 2018, at 02:11, Brent Meeker <[email protected] >>> <mailto:[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). > > And it doesn't bother you at all that our observations are all of mixtures
That is explained by the (boolean) machine theory, or arithmetic. > and never of superpositions; We observe superposition indirectly all the time. That is why we discover/postulate QM to begin with. When I observe/infer/prepare the state u-d with an u-d/u+d apparatus, I observe/infer/prepare a superposition. > because you are submerged in platonic mysticism. ? Bruno > > 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] > <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.
