> On 1 Aug 2018, at 07:49, Brent Meeker <[email protected]> wrote: > > > > On 7/31/2018 10:19 PM, Jason Resch wrote: >> >> >> On Tue, Jul 31, 2018 at 4:52 PM Brent Meeker <[email protected] >> <mailto:[email protected]>> wrote: >> >> >> On 7/31/2018 2:38 PM, Jason Resch wrote: >>> >>> >>> On Tuesday, July 31, 2018, Brent Meeker <[email protected] >>> <mailto:[email protected]>> wrote: >>> >>> >>> On 7/31/2018 9:46 AM, Jason Resch wrote: >>>> >>>> >>>> On Tue, Jul 31, 2018 at 1:11 AM Brent Meeker <[email protected] >>>> <mailto:[email protected]>> wrote: >>>> >>>> >>>> On 7/30/2018 9:21 PM, [email protected] >>>> <mailto:[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. >>>> >>>>> 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. >>>> >>>> >>>> >>>> What if the cat is on Pluto for this one hour? Would it not be perfectly >>>> isolated from us on Earth, and thus remain in a superposition until the >>>> the several hours it takes for light to get to Earth from Pluto reaches us? >>> >>> ?? Are you assuming that decoherence only occurs when humans (or >>> Earthlings) observe the event? >>> >>> >>> Brent >>> >>> >>> No, just that superposition is a relative, rather than objective notion. >> >> OK. Welcome to QBism. >> >> After reading the wiki article on QBism I still can't say I understand what >> it is about, as it doesn't seem to offer any core positions. >> >> I am an adherent of bayesianism, and believe it applies generally in all >> domains (being an agent having to make decisions/bets), so what does QBism >> add if one already accepts a general reliance on Bayes theorem? It doesn't >> seem like QBism takes any strong position on any of the quantum paradoxes, >> nor offer any insights to addressing or explaining them. In this it seems >> like a pretty empty theory, with hints towards the >> "instrumentalist" and "shut up and calculate" mindsets--that only the >> probability matters. To the extent that is true, I reject QBism. While >> QBism might not put forward anything that is false, the attitude it conveys >> seems like it would stymie progress towards advancing our understanding of >> reality. > > QBism says that QM is a theory for predicting personal beliefs. The > "collapse" of the wave function is simply updating one's beliefs based on an > observation.
That leads to the many-worlds, or its "many-minds” variants (even closer to what mechanism enforce on the interpretation of the observable). ITSTM. Bruno > > Brent > > >> >> That superposition is relative does not require observers or knowledge, it >> is a consequence of the postulates of QM. Either system A has interacted >> with system B and they are both part of the superposition together, or they >> have not interacted yet and system A will be in a superposition of various >> possible states to system B, and system B will be in a super position of >> various states to system A. >> >> Jason >> -- >> 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.
