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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In quantum experiments are we measuring the quantum state of a system or are we measuring the effect of the measurement on the quantum state?

At the macro classical world, measurements in experiments when done correctly interfere very little with the state of the system under investigation. As an example a digital ohmmeter with very high ...
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How to add markers to IR photographs

I'm using an IR camera to identify thermal patterns. The thermal images are similar to this [LINK] image. I'd like to add markers to the area being measured to determine dimensions and normalize the ...
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Trouble understanding the math of the preferred basis problem

I've been trying to understand the preferred-basis problem in QM, specifally in the Everettian intepretation. To quote an answer to another question which discusses this: In my opinion, the situation ...
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Is the uncertainity principle explained by disturbances or only by the Fourier picture?

Qualitatively, the tradeoff in uncertainty between two non-commuting observables $\hat{x}$ and $\hat{y}$, could be explained by... the Fourier picture where the more one variable is defined (i.e., ...
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Why macroscopic bodies should exist as wavepacket?

Based on my understanding, we assume that the electrons, exist as wavepackets in the solids while deriving the transport equations for transistors, we create wavepackets out of momentum eigenstates ...
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Have objective collapse theories been ruled out by recent experiments?

Have objective collapse theories been ruled out by recent experiments, such as the entanglement of macroscopic objects? (vibrating drumheads)
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I don't understand Wigner's friend paradox

The Wigner's friend experiment goes like this: Say Wigner instructed his friend to perform Schrödinger's cat experiment in a laboratory while he work from home, his friend made the measurement and ...
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Are quantum experiments superdeterministic? [closed]

Lately this recent video of Dr. Sabine Hossenfelder made me think if this theory deserves a serious review and has substantial ground. What are the rigorous arguments against this theory today? Please ...
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How is quantum "measurement" actually done?

There is a lot of talk in the fundamentals of QM about "measurement" and "observation", but never much specificity in what is going on at a basic level. For example, an electron ...
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Copenhagen interpetation applied to a video recording [duplicate]

I always get a little confused when it comes to the Copenhagen interpretation, and especially the fact that (for instance as per this article https://medium.com/science-and-philosophy/the-copenhagen-...
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Can weak measurement principles of Quantum mechanics be used in similar questions in classical estimation problems?

This is a surface level question and I don't want to go into detail. Imagine an algorithm which when used with a sensor output gives the statistical moments of a variable in nature (for example mean ...
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Spacetime of a quantum measurement

In a classical(or wave) picture, when we measure a doppler effect from a receding galaxy, we are working on two wave crests essentially. Therefore, there are two events in spacetime for such detection....
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Any unique or unified definition of measurement in physics?

I have not found any unique or unified definition of measurement in physics, and it seems that there isn't one. What is a unique or unified definition of measurement in physics?
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Kochen-Specker theorem and measurement map in the formalism of QM

There is (or rather was) a famous debate between Born and Einstein about interpretational issues of Quantum Mechanics. In this debate Einstein was advocating the so called theory of hidden variables. ...
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Uncertainty and accepted values

I had a problem that caused disagreement in my class, and its as follows: we did a measurement and we got $k = 1368 \pm 45$ and the accepted value is $k = 1300 \pm 50$ and the test we use is $$|x_{...
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I'm not seeing any measurement/wave function collapse issue in quantum mechanics

The information about a particle is contained in a vector of unit-norm called the wave function. One postulates says that this wave function is supposed to evolve with time as the particle interacts ...
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Why is there a measurement problem? [closed]

From what I understand, the measurement problem seems to be a problem of humans limitations and nothing more. It seems to be pretty egocentric. We're saying, because we can only observe one probable ...
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Does the Many Worlds Interpretation make any distinction between entangling processes and measurement?

Suppose I have a qubit in the state $\alpha|0\rangle + \beta|1\rangle$. In the many worlds/relative state formulation of QM, if I measure this qubit with a measuring device in some initial state $|\...
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Stern Gerlach and interference

I recently came across this experiment: a beam of spin 1/2 particles pass through a Stern Gerlach apparatus oriented in the z direction. After passing through it and splitting, the beams are again ...
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Does quantum mechanics tell us when the next measurement will occur?

In many interpretations of quantum mechanics, the result of a measurement is regarded as non-deterministic. However, my question is: is the time at which a measurement occurs deterministic? To be ...
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When does the interference pattern of DSE disappear as size of "projectile" is increased? [closed]

In trying to learn about Quantum mechanics (QM) from popular science books and Stack Exchange (I of course expect my knowledge to be anything but complete) I regularly come up with seemingly childish ...
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Wigner friend experiment with qbits

Suppose that in his isolated box, Wigner's friend measures a qbit in state $|→⟩=\dfrac{|↑⟩+|↓⟩}{\sqrt{2}}$ along the vertical axe. Then, he sends Wigner (who remains outside the box) a qbit in the ...
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How do Heisenberg Uncertainty and Quantum Decoherence coexist? [closed]

I have a question that's intrigued me for awhile. How do Heisenberg Uncertainty and Quantum Decoherence coexist? I know in the early days of QM, a common reaction to the measurement problem was to say ...
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Numerical Problems Based On Vernier Callipers [duplicate]

I watched a video on Vernier Calipers which gave me an understanding of how it works and how to read a Vernier Caliper. I also tried the GeoGebra simulation. But I am not able to understand the ...
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How does the precision of the measuring device affect the wave function we get instantly after a measurement on $\Psi$?

Going through David J. Griffiths' Quantum Mechanics book today, I read the following: If the operator $Q(\hat x,-i\hbar\ \partial_x)$ has a continous spectrum with eigenvector $f_y(x)$ corresponding ...
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Has there been experimental evidence that entangled state collapses simultaneously?

If we observe the observable of one particle among two particles which are entangled each other and separated far away, we can determine the value of the other particle’s same observable from the ...
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How is many world interpretation of quantum mechanics compatible with no cloning theorem?

In many worlds interpretation of the quantum mechanics all possible outcomes of a measurement are realized, however, in different universes. Everytime a measurement occurs we register one outcome and ...
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What problem is the Many-Worlds Interpretation actually solving? Is it a reframing of the measurement problem?

Before I state my question I want to say I am in no way an expert/professional in this field. I read quite a bit on the subject and I consider myself familiar with the basic concepts but I really want ...
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What is the definitive evidence we have that quantum theory's probabilistic nature is physical and not epistemic?

For example does superposition or wavefunction really occur in the physical quantum world or is it only a property of the quantum theory's framework and formalism to help us to make accurate ...
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the measurement problem, what is it that drives the wave function to collapse?

I'm hearing a lot of different solutions to the measurement problem. But what is the right answer? Does consciousness play a role in the collapse of the wave function or is there a different factor at ...
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2 votes
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On realistic interpretations of quantum mechanics - single quantum systems and measurements [closed]

I am interested in realistic interpretations (in the sense of "quantum state realism" or "wavefunction realism") of the behaviour of a single quantum system interacting with a ...
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Are there known paradoxes regarding a detector that was, before use, entangled with a particle it detects?

Is it possible to design a system where a detector is entangled with the particle state it detects (before it is detected), and to create a paradox from this? Upon observance of a state by the ...
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How could theoretical physics without experimentalists aid distinguish observer effect from Kennard's uncertainty principle?

Regarding this experiment which was carried out in 2012: https://arxiv.org/abs/1208.0034 I'm wondering how could the scientific society be totally convinced(prior to this paper being published) based ...
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Are Bohm's later books worth reading? [closed]

I mostly see Bohm's later books such as Wholeness and the implicate order and The Undivided Universe quoted in discussions of pseudoscience and quantum mysticism. Do they offer any useful insight into ...
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Measurement in 't Hooft Cellular Automation Interpretation (CAI)

In the 't Hooft Cellular Automation Interpretation it is declared, that for a system described by some template state $\lvert \psi \rangle$ and for any ontological measure outcome $\langle a \rvert$ ...
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Why is wave function collapse mysterious?

There are lots of questions and answers on this site about wave function collapse (for example, How does a Wavefunction collapse?, Why does a wavefunction collapse when observation takes place?, How ...
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Why does particle measurement cause quantum wavefunctions to collapse

When we attempt to measure a certain property of a particle, how and why does its wave function collapse? I've tried to find answers on my own, but they've been far too complicated for me to ...
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Why does commutativity mean that two observables can be measured together?

BACKGROUND As far as the Heisenberg uncertainty principle is concerned, my understanding of commuting observables $\hat{A}$ and $\hat{B}$ is that the measurement outcome $a_i$ does not perturb (or ...
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Can someone explain the measurement problem with little bit of mathematics?

Can someone mathematize the statement of the quantum measurement problem? I am only interested in the statement of the problem (and not its solutions). Thanks. Still confused. Stated in this way (as ...
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2 votes
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Does the Bell test preclude localism, realism, both, or just one of either (indeterminate)?

I saw this excerpt from the wikipedia article on EPR paradox They postulate that these elements of reality are, in modern terminology, local, in the sense that each belongs to a certain point in ...
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Can quantum measurements be the origin of thermodynamic arrow of time?

We can practically consider that the microscopic interactions are symmetric with respect to time(as we can neglect weak force for many cases which is the only interaction that can violate $T$ symmetry)...
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Determine initial permeability from experimental data

How to determine initial permeability of the sample having only its dimensions (ring with $R$ - external radius, $r$ - internal radius, and thickness $h$), the number of coils around it $N$, and only ...
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Wigner's friend experiment - How is there an apparent paradox?

Wigner's friend thought experiment mentions that there is an apparent paradox - 'when exactly did the collapse occur?'. Whether it occurred when the friend made the measurement, or when Wigner asked ...
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Wigner's friend question [closed]

This is probably a dumb question, but does anyone know whether both Wigner and Wigner's friend observe the same result once both have been in the room and measured?
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Electron interference

As I have understood, as per QM, electrons could behave as waves in a double slit experiment, i.e. form dark and bright bands, albeit after sufficient electrons have been shot from the source. Also, I ...
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Quantum measurement paradox

let's define 'a measurement device' as a system which is highly sensitive to the eigenstate of an observable. The sensitivity is quantified let's say by how irreversible and grand the small changes in ...
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Difference between Phenomenal and Phenomenological in the Context of Physics

I was going through a conference presentation on System of Systems Engineering. In the presentation entitled "Macroscopic Quantum Mechanics and the SoSE Design Approach", I came across a ...
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Why is $\Delta x$ or $\Delta p$ constant for a particular $\psi_n$?

We were asked to calculate $\Delta x \Delta p$ for the $\psi_0,\psi_1$ of the harmonic oscillator.And so we calculated the answers and verified that $$\langle T \rangle +\langle V\rangle = (n+1/2)\...
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Does the particle interfere with itself, or the observer?

In the double slit experiment, the observer doesn't know which slit the photon went through so the wavefunction is modelled as going through both slits at once and thus there's interference on the ...
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How could one ever settle with a coin flip?

Suppose that one could "flip" a coin, and that it settled onto a platform. For simplicity, let the coin processed with the nonzero angular momentum on $y$ axis only. To further simplify the ...
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