Questions tagged [wavefunction-collapse]
Wavefunction collapse amounts to the apparent reduction of a wavefunction consisting of a superposition of several eigenstates to a single eigenstate (by "observation"). It underlies measurement in quantum mechanics and connects the wave function with classical observables, in a thermodynamically irreversible interaction with a classical environment, normally disfavoring future QM interference.
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Is measurement and observation the same as processing data? [duplicate]
My understanding is that "observation" and "measurement" cause quantum wave function collapse. Can something be "measured" or "observed" without a process ...
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Is collapse of wavefunction actually relative?
I suddenly had an odd philosophical question. Suppose there are two people and the Schrodinger's cat experiment is done, such that after placing the dynamite and cat within the box and waiting for a ...
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Wavefunction collapse in a bubble chamber
When a particle enters a bubble chamber, its wavefunction collapses and the particle behaves as a classical one. Is it correct?
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The many-worlds interpretation and a free particle
How does the many-worlds interpretation understand the time evolution and spread of a free particle wave function? That is, does every continuously small change constitute a cosmic action that causes ...
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Is there an axiom for degenerate (or continuous) quantum collapse? [duplicate]
Most introductory QM texts say that measurement collapses the quantum state into one of the eigenstates of the observable's operator (and with a probability amplitude given by the corresponding ...
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Collapse postulate in the density operator formalism [duplicate]
To the extent that the collapse postulate holds, textbooks will almost invariably restrict the discussion to contexts in which states are represented by normalized kets, so that the collapse postulate ...
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Does the wave function of system plus detector satisfy the Schrödinger equation?
Let $S$ be a quantum system and let $D$ be a detector. Suppose that $D+S$ does not interact with the environment. Now when $D$ makes a measurement of $S$, the wave function of $S$ collapses. Therefore,...
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Is a quantum measurement a unitary transformation of the entire system? [duplicate]
When we measure a quantum particle, its wavefunction collapses to an eigenstate. This is not a unitary transformation.
However, measuring a particle neccesarily involves the particle interacting with ...
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Is the measurement problem an interpretation or practical problem?
According to Wikipedia:
In quantum mechanics, the measurement problem is the problem of how, or whether, wave function collapse occurs.
Is the measurement problem an interpretation problem or a ...
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Can gravity cause a wave function to collapse?
Assume the Copenhagen interpretation.
Suppose that a particle, for example an electron, has a wavefunction. If a heavy object, like the Earth, is close by, then that object interacts with the electron ...
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How much does the collapse of the wave function reveal about the state of the quantum prior to collapse?
The best way I can pose this question is through an example: suppose a photon passes through a beamsplitter, putting the photon into a superposition of the two paths (reflected or passed through), and ...
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Does an electron's wave function collapse when it emits a photon?
I've been wondering how electromagnetic interactions between electrons are calculated if the position isn't determined until the wavefunction describing position collapses.
Does the wavefunction need ...
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Quantum wave function collapse by unknown observer [closed]
If there's an "unknown" third-party observer of a particle, that would collapse the wave function for the first party, but has that "ever" happened, without knowing who the ...
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Double slit question - wavefunction collapse
If we fire photons at the double slit, we see an interference pattern on the screen. We know that if a quantum system interacts with any outside object (such as a detector, etc), its wavefunction ...
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Where no observer exists, does this mean the wavefunction never collapses?
In most places across the universe, there is no conceivably sentient candidate to act as an "observer" to this system.
Are we to believe that, in the emptiness of intergalactic space, or ...
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Who caused first collapse of wave function?
With my wife we discuss a quantum theory and wonder whether a wave function could collapse without an observer - meaning a human/or any other living beings.
If so we could make a conclusion that there ...
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Meaning of eigenvalue of the position operator $\hat{x}$?
Apologies for asking a question which may be too basic. I understand at the conceptual level that a measurement collapses a wavefunction into a single spike, which will then evolve again immediately ...
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Assuming Wave Function Collapse Actually Exists, Can a Wavefunction Collapse into Another Wavefunction that is not the Delta Function
Suppose we have a time independent potential and suppose $\psi_1(x)$ and $\psi_2(x)$ are two stationary states of the potential with energies $E_1$ and $E_2$. Suppose the wavefunction is
$$
\Psi(x,t) =...
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Simultaneous measurements of two entangled particles [duplicate]
Experimental evidence reject the local hidden variable theory, so let's say quantum mechanics is right and the wave function does instantaneously collapse upon measurement.
Suppose we have two ...
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What is an agent in the Quantum Bayesianism/Relational Quantum mechanics-like interpretations?
In interpretations like Quantum Basyesianism, Relational interpretation, Information Theory interpretation, etc, the wavefunction represents the probabilistic knowledge that an agent holds about a ...
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Can we measure a lower limit of the velocity with which a quantum mechanical wave function collapses?
According to the Copenhagen interpretation of quantum mechanics, a wave function collapses immediately and everywhere. This seems to imply that this happens at an infinite velocity. However, if the ...
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Does a radio receiver "collapse" a radio wave function?
Does a radio receiver "collapse" a wave function when listening to a radio broadcast generated via a transmitting antenna?
Background:
There has been much discussion on this forum (here) ...
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Meaning of the transition amplitudes in time dependent perturbation theory
Consider a time dependent Hamiltonian
$$\hat{H}(t)=\hat{H}_0+\hat{V}\tag{1}\label{1}(t)$$
where $\hat{H}_0$ is the unperturbed Hamiltonian, for which the eigenvalue problem has been solved
$$\hat{H_0}\...
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Can an operator acting on a wave function be equal to taking a measurement?
I'm aware in general when an operator acts on a quantum wave function it is not the same as taking a measurement ie the hamiltonian acting on a superposition state will not give a constant multiplied ...
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Is my interpretation of the underlying idea behind this 2022 Nobel Prize story “How physicists proved the universe isn’t real” more or less accurate?
I’m not very good at math but I frequently watch PBS Spacetime on YouTube to try to satisfy my curiosity about physics despite that.
In a recent video by Dr Ben Miles titled “How Physicists Proved the ...
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What is so special about the “wave function collapse”?
Im not entirely sure of my intuition behind this topic, so please someone explain to me. Is the “collapse of the wave function” not just a description of observing an outcome? Why is there this notion ...
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What is the proof of Davies theorem: if a map on pure quantum states transforms equivalent ensembles to equivalent ones, then the map is unitary?
In the following paper (Dynamical Reduction Models by Bassi and Ghirardi), at the end of section 5.3, the following claim is made.
Consider a bijective(*) map on pure states (not necessarily unitary ...
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Is the Born rule a red herring in explaining the measurement problem? [closed]
Many explanations of the measurement problem try to derive the Born rule from Schrodinger evolution, for example Many worlds. I have two reasons to think the Born rule isn't fundamentally related to ...
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Have physicists yet ruled out if wavefunction collapse happens due to the potential from the measurement apparatus?
Suppose there is an electron in a state $|\psi \rangle$, and there is a measurement apparatus whose atoms have a joint wavefunction $|m\rangle$. In experiments, we always know the initial value of $|\...
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Does the scattering wavefunction collapse "part-by-part"?
By "scattering wavefunction", I mean the wavefunction of the scattering product prior to measurement. This thing has a non-definite particle number, as well as a non-definite particle type.
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Postulate of wave function collapse and entanglement
Can we say that a measurement on a system of $k$ entangled particles is the cause of the collapse of the wave function into $k$th states simultaneously?
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What is the ratio between particles with an uncollapsed wavefunction and particles with a collapsed wavefunction? [closed]
I wonder what the ratio between particles with an uncollapsed wavefunction and particles with a collapsed wavefunction is.
On earth, in a galaxy or in the universe.
Or is better to say:
What is the ...
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The state at wave function collapse [duplicate]
In the double slit experiment, why does the wave function collapse into the coordinate base? Why not into something else? How does the particle know that its position is measured (hence, it gets "...
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Have we actually verified the claim that macroscopic objects collapse wavefunctions?
Copenhagen interpretation claims this, but have we actually verified this? There exist two options:
Objective collapse: Consider a large isolated box inside which there is a macroscopic classical ...
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Wave Function Collapse and the Dirac Delta Function
When the wave function of a quantum system collapses, the probability of finding it at some specific point is given depends on $||\Psi||^2$:
$$
\int_{\mathbb{R}^3}{d^3 \mathbf x \; ||\Psi||^2} = 1
$$
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Understanding the Measurement Problem - Is this a good analogy? [closed]
I have asked the question in a better way: Does Vantage Point explain Bell's Inequality's Experimental Results?
This question may remain closed.
It can be head-melting to conceive of many ...
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Isn't it inaccurate to use the Schrödinger equation to find the probability that a macroscopic object will undergo quantum tunneling?
Since Schrödinger's equation doesn't show wavefunction decay or quantum decoherence, isn't it inaccurate to calculate the probability that a person or macroscopic object will quantum tunneling? I ...
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Quantum entanglement
Suppose we have two particles with entangled eigenfunctions. Let's say they are in two different regions of space, with different local Hamiltonians. Now we measure one of them, therefore the other. ...
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Quantum entanglement information through time of collapse
(I've tried my best to find an existing question that asks this question exactly)
From what I understand, given two entangled particles, one held by Alice and one by Bob, when a measurement is done by ...
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Is measurement or interaction what collapses that wavefunction?
I'm very confused about what exactly causes the wavefunction collapse. I was under the impression that quantum objects propagate as waves and interact as particles. That is, upon interaction with ...
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The collapse of Wave function isn't a physical process - but then why hasn't everything blurred into complete uncertainty?
Sabine Hossenfelder very coherently points out the "The real problem with quantum mechanics" in
the following clip: https://www.youtube.com/watch?v=LJzKLTavk-w&t=583s
Shortly after ...
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Is there a natural principle that forbids real wavefunction collapse?
The wavefunction evolves unitary. We can apply a unitary evolution operator containing the Hamiltonian (which shows the relation between time and energy). This evolution is smooth and continuous. And ...
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Continuous Collapse Interpretation
Suppose we interpret quantum mechanics to mean that the collapse randomly happens at every single moment.
Wouldn't this be identical to the many worlds interpretation except much less objectional ...
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Does quantum tunneling result in the collapse of the wave function?
Does quantum tunneling itself result in the collapse of the quantum object's wave function? So, as a hypothetical scenario, suppose you have a two-slit experiment, but instead of two slits, you have ...
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Is somebody familiar with the Continuous Spontaneous Localization (CSL) model of collapse? Is this model trustable?
The Continuous Spontaneous Localization (CSL) model of collapse was originally invented by Ghirardi, Rimini Weber and Pearle. This model tries to mimic the wave-function collapse. But is it trustable? ...
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Does information disappear when a wavefunction collapses?
The wavefunction of a particle evolves with time in a manner strictly defined by the Schrodinger equation and the local environment. The wavefunction can become very complicated (e.g. a photon trapped ...
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Wavefunction superposition state
Before measurement the wavefunction of a quantum particle, eg an electron, evolves in a superposition state. Can the following wavefunction
$$\Psi = 1\,\,\lvert \uparrow \rangle + 0 \,\,\lvert \...
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Are non-linear extensions to QM equivalent to time travel?
I recently learned of the existence of Objective Collapse theories which add non-linear terms to QM to explain wave function collapse. Per the 2014 paper Treating Time Travel Quantum Mechanically, the ...
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Collapse of state vector for degenerate eigenvalues
Consider a state vector given by
$$|\psi\rangle=a|w_1\rangle + b|w_2\rangle+c|w_3\rangle$$
where $|w_1\rangle,|w_2\rangle$ and $ |w_3\rangle$ are orthonormal eigenstates of an observable operator $\...
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Can observation by animals collapse the wave function?
In Schrodinger's cat, somehow the cat is dead and alive at the same time until someone opens the box, observes that cat's state, and collapses the wave function. Of course, something can't be dead and ...
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