Mithuna Yoganathan on The True Meaning of Schrodinger's Cat

My comment:

A measuring device only measures a measurable quantity though, and a probability, even if it is 1, i.e. a certainty, is not actually something you can measure directly without doing a large number of measurements and gathering statistics that represent the measured values. The super-position states can therefore never be known empirically. So when you say that "we" know the cat is both dead and alive, that is not empirical knowledge, it is deductive inference based on the theory that quantum states in a Hilbert space have some sort of physical reality independent of the actual observations that are made in a laboratory. To me this makes good sense, and it shows that the wave-function collapse is a condition of empirical knowledge. We simply cannot make sense of a measuring device that gives self-contradictory readings when used to measure some states of a system. But it is hard to make such an argument when the lecturer freely switches between speaking about a state of the system and a measurement as if these two things are identical!

It turns out that this is traditional in Quantum Mechanics, since at least the fifties when Julian Schwinger produced the Dirac formalism from some postulates about selective measurement, or filtration. See the end of Section 1.4.1 on page 23 of the Third Edition of Sakurai's  Modern Quantum Mechanics. Selective measurements are ones where you decide not to observe some part of the state and assume that rest of the state is definite, for example, by closing one of the slits in the double-slit experiment. Your argument then rests on where the slit isn't! "What slit?", you ask? I don't know, the one that isn't there! "What do you mean by there?" Don't be obtuse!

I have a feeling that one could explain this with some well-written Standard ML code, but that part of my brain doesn't work very well anymore. The idea is that you write a program that evolves the state without making any assumptions about the particular measurement basis, until you instantiate those parameters with some definite orientation. Then you ought to be able to experiment with observations done in different orders and get the same results you observe with light sources and photodetectors.

See Mithuna Yoganathan - Quantum Mechanics Course (and Vandana Shiva on Quantum Thinking).

Reminds me of something I wrote to my daughter:

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But the looking glass is a bit wonky! See Self-portrait: