The wavefunction-collapse tag has no wiki summary.
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Partial Measure Probability
Let be a
$$|\psi\rangle = \dfrac{3}{5\sqrt{2}}|00 \rangle- \dfrac{3i}{5\sqrt{2}}|01 \rangle+ \dfrac{2\sqrt{2}}{5}|10 \rangle - \dfrac{2\sqrt{2} i}{5}|11 \rangle$$
state with two qubits. ...
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What does the Copenhagen interpretation say about the position of a particle before measurement?
Suppose there is a particle in space. When we measure the position of that particle, we get a particular value with a probability that can be calculated from the wave function. But, according to the ...
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Does the collapse of the wave function increase entropy of the atomic system itself?
Does wave-function collapse cause the entropy of the atom (ie. the sub-atomic particle system that makes up the atom) to increase?
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How do we show that no hidden variable theories can replace QM?
I've always hit two big stumbling blocks in conceiving of the proof or disproof of hidden variable theories as being even valid idea, let alone an answerable question... I feel I must be ...
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Meaning of $\int \phi^\dagger \hat A \psi \:\mathrm dx$
While analysing a problem in quantum Mechanics, I realized that I don't fully understand the physical meanings of certain integrals. I have been interpreting:
$\int \phi^\dagger \hat A \psi ...
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Is Schrödinger’s cat misleading? And what would happen if Planck constant is bigger?
Schrödinger’s cat, the thought experiment, makes it seem like as if measurement can cause a system to stop being in a superposition of states and become either one of the states (collapsed).
So does ...
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According to wave function collapse you only have one outcome, so what happens to the other superpositions?
If the superpositions of a wave function are not needed because only one of the superpositions is allowed, what happens to the eigenvalues of the "null" superpositions?
Is the energy transferred ...
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How is wavefunction probability redistributed after partial wavefunction collapse?
Suppose I set up the double-slit experiment using photons as my particle. Behind the left slit I place a beam splitter that points some of the light off in the direction of a camera (represented as ...
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Does quantum mechanics predict instantaneous action at a distance even without entanglement?
The suggestion that quantum mechanics implies that instantaneous action at a distance occurs is normally based on the contention that this follows from the entanglement of particles that share a ...
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Does every measurement correspond to an eigenstate of an observable?
In the postulates of quantum mechanics, physical observables are described by Hermitian matrices on the state space of a system.
In another of my questions, the measurements of Rydberg-Ritz spectral ...
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What constitutes an observation/measurement in QM?
Fundamental notions of QM have to do with observation, a major example being The Uncertainty Principle.
What is the technical definition of an observation/measurement?
If I look at a QM system, it ...
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Decoherence and collapse
It is said that the decoherence does not solve the problem of measurement and/or the emergence of classicality, can somebody explain it with simple analogies or in a manner accessible to a ...
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Spike when wavefunction collapses
So, when wavefunction collapses, there is a spike occuring. Does this mean that there are parts with the continuous probability of 0? (For example, x position from -9 to -3 has probability of 0, while ...
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If I go to the church of the greater Hilbert space, can I have Unitary Collapse?
Actually, unitary pseudo-collapse?
Von Neuman said quantum mechanics proceeds by two processes: unitary evolution and nonunitary reduction, also now called projection, collapse and splitting.
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4answers
640 views
Why does observation collapse the wave function?
In one of the first lectures on QM we are always taught about Young's experiment and how particles behave either as waves or as particles depending on whether or not they are being observed. I want to ...
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When do the von Neumann projections occur and what causes them?
(Transferred as a separate question from comments in Scott Aaronson’s gravitational decoherence question)
Reversing gravitational decoherence
The modern answer seems to be that they never occur, ...
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Can you count “collapses”? How many collapses in the observable universe?
If that’s too hard, how many collapses in 100 cc’s of boiling water in one second?
In biology, the very first robin that is scientifically described is preserved and called the “type robin”. The ...
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Is it the act of measuring a quantum particle that causes it to lose its uncertainty?
I have designed an experiment. Without going into detail it resolves around the double slit quantum eraser experiments. If we can infer the location of a particle without actually measuring it, does ...
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wavefunction collapse and uncertainty principle
We all know that wavefunction collapse when it is observed. Uncertainty principle states that $\sigma_x \sigma_p \geq \frac {\hbar}{2}$. When wavefunction collapse, doesn't $\sigma_x$ become $0$?, as ...
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Matter wave of multiple particles of different types
I am slightly getting confused on the following issue:
When performing double-slit experiment of electrons, a screen allows the matter waves to be detected as particles. And as we all know that ...
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In which way is decoherence not symmetric between the two considered systems?
If a quantum system interacts with a "big" quantum system, you have dephasing.
The models of decoherence all have this atog aproach to them, about what is to understood of the interaction of the ...
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How to observe a particle with indefinite position?
As I understand it, when physicists talk about something behaving both like a particle and a wave, what they mean is that it has momentum like a particle, but its position is determined ...
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4answers
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Non linear QM and wave function collapse
I heard that there have been some propositions about describing the collapse of the wave-function by adding non-linear terms, but I couldn't anything in any any textbooks or even articles (probably ...
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Quantum Entanglement - Measuring Twice
In the answer here and on the wiki article and many other articles it is mentioned that if one of 2 entangled particles is measured their state collapses according to the Copenhagen interpretation.
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Is the collapse of the wave function inherently time asymmetric?
Schroedinger's equation, as we all know, is time symmetric. In quantum field theory, we have to come up with a more sophisticated CPT reversal, but the essential point remains unchanged. However, the ...
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Does measurement, quantum in particular, always increase the total entropy?
Measurement of a quantum observable (in an appropriate, old-fashioned sense) necessarily involves coupling to a system with a macroscopically large number of degrees of freedom.
Entanglement with this ...
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What does the appearance of a classical particle fundamentally reduce to?
I've been reading an article that describes what seems to be a classical particle as a regularity in the global wavefunction over a quantum configuration space:
When you actually see an electron ...
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Entanglement and the double slit experiment
Is the double slit experiment an example of entanglement when it seems as if the photon is going through both slits? Or put another way, is it at this stage when we attempt measurement we see a photon ...
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5answers
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How isolated must a system be for it's wave function to be considered not collapsed?
As an undergrad I was often confused over people's bafflement with Schodinger's cat thought experiment. It seemed obvious to me that the term "observation" referred to the Geiger counter, not the ...
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Can the time direction of wave function collapse be reversed?
The laws of physics are invariant under CPT transformations reversing time, inverting space and flipping charges. Almost so. The collapse of the wave function is the odd man out. Can the time ...
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Non-unitarity of wave function collapse
Why the wave function collapse corresponds to a non-unitary quantum operation?
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Stochastic processes and wavefunction collapse
Some time ago I had an idea that, as the unitary evolution of the wavefunction is described by a deterministic equation (PDE, simply), could be the collapse of it be described by some kind of a ...
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Minimum criteria for quantum state dissolution
What are the minimum conditions required to cause the colapse of the quantum state ? Or, what forces/equations determine when an object (for instance an electron) is forced out of its quantum state in ...
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On the nature of the collapse of the wave function
The collapse of the wave function by measurements is one of the most mysterious properties of quantum mechanics.
At what scale does the wave function collapse? What are the conditions for a ...
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Eigenvalue Postulate and Experiment Outcomes in QM
In Nielsen and Chuang's text on Quantum Information and Computation, the measurement postulate is stated by using a collection of measurement operators and the outcomes are the indices of the ...
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Is there a difference between observing a particle and hitting it with another particle?
First, let me state that I'm a lot less experienced with physics than most people here. Quantum mechanics was as far as I got and that was about 9 years ago, with no use in the meantime.
A lot of ...
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What is the difference between a measurement and any other interaction in quantum mechanics?
We've learned that the wave function of a particle collapses when we measure a particle's location. If it is found, it becomes more probable to find it a again in the same area, and if not the ...
