Questions tagged [measurement-problem]
DO NOT USE THIS TAG just because your question involves measurements (either quantum or classical). The measurement problem asks how wave function collapse occurs during measurement in quantum mechanics, and how it can be reconciled with unitary evolution.
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Why can't we measure non-linear operators in QM using single shot measurements?
Consider an operator like the modular Hamiltonian $K$ defined by $$\rho=e^{-K}$$ where $\rho$ is some (reduced) density matrix. So $K$ depends non-linearly on $\rho$ in general. It can be shown that ...
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Does quantum mechanics derive statistical independence for repeated measurements, or is it an assumption beyond the Born rule? [closed]
In standard quantum mechanics, the Born rule gives marginal probabilities for individual measurement outcomes, such as $P(\uparrow) = P(\downarrow) = 1/2$ for a qubit in the $|+\rangle$ state measured ...
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How does the path integral for the Universal Wavefunction account for future internal decoherence events?
I'm trying to solidify my understanding of the path integral formalism when applied to the entire universe, and I've run into a conceptual point that I'd like to clarify.
Let's assume a purely ...
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What happen with wavefunction immediately after a measurement?
One of the postulates of quantum mechanics, introduced by Dirac, says that immediately after a measurement of an observable $\hat A$ the wavefunction abruptly becomes an eigenfunction of $\hat A$. In ...
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Do quantum entities lack definite positions because of measurement limits, or is it a fundamental feature of nature? [duplicate]
In quantum mechanics, particles such as electrons do not have a fixed position until they are measured
Questions:
Is this indeterminacy simply due to the limitations of our current measurement ...
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Wave Function and Measurement (Landau-Lifschitz Volume 3)
I believe Landau is trying to motivate the collapse of a wavefunction. However, there are some parts which are confusing.
He claims that the apparatus is in an initial state $\Phi_0(\xi)$ while the ...
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Is the collapse of the wavefunction really part of the quantum theory?
The collapse of the wavefunction by comparing it with the Schrodinger equations has some differences: it is higly non-linear while the Schrodinger equation is linear, it is non-local as proven by Bell'...
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Does the collision between two molecules count as a "measurement"?
When two reactant molecules collide in a reaction (according to the collision theory of chemical kinetics) do their wavefunctions collapse? That is, does the collision count as a measurement? If they ...
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Quantum measurement when passing through a slit?
Consider a quantum particle like an electron or photon that hits a screen (say it's fluorescent, or generally involves some interaction with one or few atoms to isolate the location) that can ...
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Multimeter cannot read the capacitance
I am making a DIY Paralel Plate Capacitor with the dimension of 27.5cm times 4cm seperated by 80 gsm paper. Assuming paper thickness is 0.1mm I should get around 3.6nF.
But when I test using my cheap ...
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To what degree should macroscopic objects be in superposition of position states according to standard quantum theory?
In this review article on objective collapse theories, which is also linked from this Phys.SE post, at least in the part I've read so far, a deal of fuss seems to be made about the fact that we don't ...
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How much can an observer know about its own quantum state?
Let me state my background: I am familiar with the usual formalism of QM, of how measurements are modeled, measurement problem, decoherence, etc.
In thinking about the process of measurement, I was ...
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Continuous Sample Paths for distributions determined by Schrodinger equation?
Let us first recall how Brownian motion is described in pure mathematics. For all $t\in [0,\infty)$, we have a probability distribution $\mathscr D_t:= \text{Normal}(0,t)$, and random variables $B_t$ ...
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Uncertainty of measurement in Bohmian mechanics
Let's have two non commuting operators $\hat A$ & $\hat B$ corresponding to the physical quantities $A$ & $B$. Also let's assume we are given a wave function $\Psi(\vec{r})$. Because $\hat A \...
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Solution to the measurement problem - explanation
Has the measurement problem been resolved? Could someone explain the current state-of-the-art understanding of why deterministic evolution results in a random measurement outcome? Is there a model ...
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