On Thursday, October 24, 2019 at 4:53:00 PM UTC-6, Philip Thrift wrote: > > On Thursday, October 24, 2019 at 5:07:34 PM UTC-5, Alan Grayson wrote: >> >> On Thursday, October 24, 2019 at 12:56:29 PM UTC-6, Philip Thrift wrote: >>> >>> On Thursday, October 24, 2019 at 9:27:14 AM UTC-5, Alan Grayson wrote: >>>> >>>> On Monday, October 21, 2019 at 6:21:26 PM UTC-6, Alan Grayson wrote: >>>>> >>>>> On Monday, October 21, 2019 at 12:03:20 AM UTC-6, Brent wrote: >>>>>> >>>>>> >>>>>> On 10/20/2019 10:46 PM, Alan Grayson wrote: >>>>>> >>>>>> On Sunday, October 20, 2019 at 6:35:10 PM UTC-6, Brent wrote: >>>>>>> >>>>>>> >>>>>>> On 10/20/2019 4:58 PM, Alan Grayson wrote: >>>>>>> >>>>>>> On Sunday, October 20, 2019 at 11:35:13 AM UTC-6, Brent wrote: >>>>>>>> >>>>>>>> >>>>>>>> On 10/19/2019 6:56 PM, Alan Grayson wrote: >>>>>>>> >>>>>>>> Sean says the decoherence time is 10^(-20) sec. So when the box is >>>>>>>>> closed, the cat is in a superposition of alive and dead during that >>>>>>>>> time >>>>>>>>> interval, assuming the decay hasn't happened. If that's the case, I >>>>>>>>> don't >>>>>>>>> see how decoherence solves the paradox, unless we can assume an >>>>>>>>> initial >>>>>>>>> condition where the probability of one component of the >>>>>>>>> superposition, that >>>>>>>>> the cat is dead, is zero. Maybe this is the solution. What do you >>>>>>>>> think? AG >>>>>>>>> >>>>>>>> >>>>>>>> Maybe this is an easier question; after decoherence, assuming the >>>>>>>> radioactive source hasn't decayed, what is the wf of the cat? Is the >>>>>>>> cat >>>>>>>> in a mixed state, alive or dead with some probabIlity for each? AG >>>>>>>> >>>>>>>> >>>>>>>> You can't "assume the radioactive source hasn't decayed". The >>>>>>>> point Schroedinger's thought experiment is that when the box is closed >>>>>>>> you >>>>>>>> don't know whether or not it has decayed and so it is in a >>>>>>>> superposition of >>>>>>>> decayed and not-decayed and the cat is correlated with these states, >>>>>>>> so it >>>>>>>> is also in a superposition of dead and alive. >>>>>>>> >>>>>>>> Brent >>>>>>>> >>>>>>> >>>>>>> I thought you might say this. OK, then what function does >>>>>>> decoherence have in possibly solving the apparent paradox of a cat >>>>>>> alive >>>>>>> and dead simultaneously. TIA, AG >>>>>>> >>>>>>> >>>>>>> It doesn't necessarily solve "that problem". Rather it shows why >>>>>>> you can never detect such a state, assuming you buy Zurek's idea of >>>>>>> envariance. One way to look at it is it's the answer to Heisenberg's >>>>>>> question: Where is the cut between the quantum and the classical? Once >>>>>>> envriance has acted, then the result is classical, i.e. you can ignore >>>>>>> the >>>>>>> other possibilities and renormalize the wave function. >>>>>>> >>>>>>> Brent >>>>>>> >>>>>> >>>>>> Woudn't you agree that if the system, in the case a cat, goes >>>>>> classical after 10^(-20) sec, its state must be a mixture at that point >>>>>> in >>>>>> time even if the box hasn't been opened? AG >>>>>> >>>>>> >>>>>> In MWI it's only a mixture FAPP. But if you haven't opened the box >>>>>> (and Schroedinger was assuming an ideal box) you don't know whether the >>>>>> cat >>>>>> has "gone classical" or not. So your representation of its state is >>>>>> still >>>>>> a superposition. That's the QBist interpretation. The wf is just what >>>>>> you >>>>>> know about the system. >>>>>> >>>>> >>>>> Please remind me; if the wf is a *superposition* before the box is >>>>> opened, what exactly does this mean? That is, what does *interference* >>>>> mean in this circumstance? TIA, AG >>>>> >>>> >>>> Please indulge me on this. At this point I have no clue what >>>> superposition and/or interference means in this context. TIA, AG >>>> >>> >>> >>> All these are couched in the vocabulary of the formulation and >>> interpretation of the theory one begins with, and so they have ambiguous >>> meanings. >>> >>> @philipthrift >>> >> >> Can you answer the question assuming the CI? AG >> > > > > Just translate this into "CI", in whatever terms you like. It gives the > same answers, so what difference does it make? > > *The probability P for an event to occur is given by the square of the > complex magnitude of a quantum amplitude for the event, Q. The quantum > amplitude Q associated with an event is the sum of the amplitudes > associated with every history leading to the event.* > > [This] specifies how probabilities are to be computed. *This item builds > the concept of superposition, and thus the possibility of quantum > interference, directly into the formulation.* Specifying that the > probability for an event is given as the magnitude-squared of a sum made > from complex numbers, allows for negative, positive and intermediate > interference effects. This part of the formulation thus builds the > description of experiments such as the two-slit experiment directly into > the formulation. A history is a sequence of fundamental processes leading > to the the event in question. > > http://muchomas.lassp.cornell.edu/8.04/Lecs/lec_FeynmanDiagrams/node3.html > > > @philipthrift >
Sorry, I really don't get it. For me "interference" refers to waves which cross each other and add their amplitudes, positively and negatively. Why, if we give a probability interpretation to the amplitudes, does this have anything to do with interference, particularly for a wf for S's cat which is entangled with the wf of a radioactive source? AG -- 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 view this discussion on the web visit https://groups.google.com/d/msgid/everything-list/c3418bf6-58f5-41a6-862f-8f5337c9115f%40googlegroups.com.
