Measurement apparatus Definition and 13 Threads

I have some doubts regarding my personal interpretation that i was contemplating about in the context of Wigner's friend experiment (also tested in the laboratory recently). Could it be that a system is always in a superposition, and when we perform a measurement, we obtain a definite value due...

Basic descriptions of spin such as the beginning of Lindley's "Where does the weirdness go" state that an electron's spin doesn't exist or is "indeterminant" until measured (e.g. passed through a Stern-Gerlach field). However, isn't the magnetic field nonzero essentially everywhere (albeit...

Question --- So I've done a calculation which seems to suggest if I combine the system of a measuring apparatus to say an experimenter who "reacts" to the outcome of the the measurement versus one who does not. Then the change in entropy in both these situations is bounded by: $$ \Delta S_R...

What exactly is a measurement device and how does it carry out a measurement? For instance, in the double slit experiment, you always hear about particle/wave duality. When it's not being measured it behaves like a wave but when a measuring device is placed by the slits, it behaves like a...

This is related to the thread "Is quantum theory a microscopy theory?" discussed mostly by Ph.Ds. I make this new thread so as not to disturb the experts discussions or even hijack or close it prematurely. In message #27 of...

Spec My job, as an undergraduate EE student, is to create a test rig for offsite electronics (environmental sensors hooked up to a data logger, 12V batteries and solar panels). The test rig should be able to evaluate output from sensors (serial TTL, analog voltage, 1-wire) and output required...

Suppose we have a quantum system ##Q## with an initial state ##\rho^{(Q)}##. The measurement process will involve two additional quantum systems: an apparatus system ##A## and an environment system ##E##. We suppose that the system ##Q## is initially prepared in the state ##\rho_{k}^{(Q)}## with...

I have encountered this paper "Curie Wiess model of the quantum measurement process". https://arxiv.org/abs/cond-mat/0203460 Another work by the same authors is "Understanding quantum measurement from the solution of dynamical models" https://arxiv.org/abs/1107.2138 I am still evaluating the...

Any suggestion on a good (but as usual not that expensive) scale that can measure at least to centigram precision? Searching online (e.g. Amazon) I did find some options but the reviews are usually mixed regarding precision (users will say that scales with milligram precision specs are not that...

hey, i am a sophomore engineering student and i was looking to make a project this summer, for some extra credit, so i had in mind a device that measures force in certain situations, as an example if we have a machine ( with pulleys and machines) with 2 sides, one side is where the force is...

Does measuring a polarized photon after it passed a polarization filter put the measurement apparatus in a superposition of detected/not-deteced (the photon)? Does this depend on whether the photon is part of an entangled pair?

I'm nearly at the end of my preliminary testing for a wind tunnel in my A2 physics coursework. My question for my project so far is: "Do different shaped objects exhibit different properties under the influence of high speed air". For my coursework I need to measure or observe something to get a...

I was wondering about decoherence: Suppose a measuring apparatus measures a single quantum property (say, spin). After the actual measurement of the property has taken place, the result 'decoheres' into the apparatus until the apparatus shows the measurement result, after which it decoheres...