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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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The equations of classical physics are time reversible -- unchanged when $t$ is replaced by $-t$. The Schrodinger equation in quantum mechanics is time reversible -- unchanged when $t$ is replaced by ...
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When we measure the position of a particle,it collapses to a new wavefunction which is a dirac delta function.It's probability density spikes at a particular position value.So when we measure its ...
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Is it really the act of conscious observation that collapses the wave function, or could it be the presence of additional measurement apparatus eliminates the interference pattern independent of a ...
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In a beam splitter experiment with a single photon, if I place a detector on one path and after some time it never clicks, why does the wavefunction still collapse to the other path even though I ...
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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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I did my PhD research on device physics of optoelectronic devices. We take the square of $\langle f| H_{int} |i\rangle $ as the photon absorption probability or the theoretical efficiency of a ...
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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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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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As far as I understand as a layman (and forgive me if I say anything wrong, I am merely stating my current understanding), quantum mechanics predicts outcomes based on a wave function, which is a ...
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I was introduced to the objective wavefunction collapse by dr.Sean Caroll. He explains that objective wavefunction collapse theories say that after some finite time the wavefunction of a electron ...
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In quantum mechanics it is said that a measurement collapses the wave function while perturbation changes the hamiltonian but how a system knows if my interaction with it is just a perturbation or a ...
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When we measure the position of an object its wavefunction collapses to infinity at a particular point. So if we continuously measure the position of the object it will give same value continuously. ...
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I have a pretty solid understanding of ordinary quantum mechanics, but I’m hitting a conceptual block about quantum field theory. My understanding is that we are creating a wavefunction of possible ...
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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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Lets say there are two entangled Qubits A, B, very far away from each other and described by the state $|\Psi\rangle = |++\rangle + |--\rangle$ In a reference system S, A measures + and one hour ...
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In the standard double-slit experiment, placing a detector at one slit causes the wavefunction to collapse, preventing an interference pattern. I am exploring whether wavefunction recovery is possible ...
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I've been thinking about the quantum measurement problem and have come up with a perspective on the observer's role in collapsing a quantum superposition. Traditionally, it's believed that an observer ...
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I am trying to understand basics of quantum mechanics. I apologize for my obtuse thinking and tedious notation. Suppose that I have some quantum mechanical system with Hamiltonian $H$. Assume that ...
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I have been going through Shankar's QM book. In Chapter 4 under the topic of "How to Test Quantum Theory", he proposed that first of all we need to have a well known quantum state and for ...
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I have heard the following claims: The collapse of the quantum wavefunction can be shown mathematically to be truly nondeterministic. We know of no other physical phenomenon that is truly ...
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This can be viewed as a follow up to this/this questions about an apparent inconsistency between the notion of wavefunction collapse and relativity. The setup is simple: two entangled systems are ...
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I have a real problem with understanding this one. Suppose you are taught in some school, without access to experiments, just theory, the many-worlds interpretation of physics. So that's all you have, ...
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Say we have 10 electrons in a box. If we measure the spin of an individual electron along some axis, we find it to be spin up or down, but not in between. But what if we measure the combined spin ...
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If you want to study 1 electron, it is described by wavefunction $\psi(x, y, z, t)$ and its evolution is dictated by Schrodinger equation. If you want to study its interaction with another electron, ...
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There is a system with two particles in a state given by the wave function $F(x_1,x_2)$. What does it mean to make a measurement on one of the particles? This is not defined among the axioms of ...
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There is a particle source, which emits particles (e.g. radioactive decay). It is supposed that the wave function is spherical. The process is isotropic. If I put two detectors (A and B) at distance R ...
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Which of these is understood to be the relationship between classical and quantum mechanics? Or is it a mixture of these, or something else entirely? The classical world comprises of measurement ...
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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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From the Heisenberg uncertainty principle, we know that we can't know both the position and momentum of a particle, does this mean that measuring the position puts the momentum in a superposition? Or ...
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Suppose we have a wavefunction of a single particle in a potential. We measure it's position. After collapse the wavefunction collapses to a single eigenstate of position. This means that the ...
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Why are there no clear experiments describing the exact boundary between classical and quantum sizes? Assuming we believe in interpretations of quantum mechanics (QM) that state during measurement (...
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I apologise in advance if this question seems ignorant Before measurement, a particle can exist in multiple states simultaneously. However, when an observation is made, the wave function "...
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I apologize as I am new to Quantum Physics and Wheeler's Delayed Choice experiment, I have some questions that I think any newbie like me would also come up with, and I would really appreciate any ...
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Some interpretations of quantum mechanics support the conclusion that, from the perspective of an experimenter, the state of the universe evolves unitarily until the experimenter observes the outcome. ...
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Let us assume a continuous wave function. Suppose we make a measurement of the position of the particle and obtain as a result the interval $(x_0-\delta, x_0+\delta)$. $\delta>0$ stays for the ...
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Let's take the double-slit experiment for example, the stream of particles shot through the slits show different patterns on the detector depending on whether the particles have been observed to pass ...
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Let $\psi \in \mathcal{H}$ be a (pure) state of some physical system and suppose we measure an observable $A$ (represented as self adjoint (say bounded) operator, i.e. an element of $\mathcal{B}(\...
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Apologies for the additional question on a topic that seems to be queried relatively frequently in this forum - I was unable to find an explicit answer to this specific question in searching physics ...
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Let us consider a particle in a one-dimensional space (X-axis) whose state, at a given instant of time, is described by a given wave function. Let us assume that we measure the momentum p using a ...
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I am struggling to understand the nature of observations in quantum mechanics. My understanding is the following. Properties of quantum objects are determined by a wave function. This wave function ...
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In experimental laboratories, every measurement of the position of a particle always returns an error, which can be very small, but is never zero. Is this because our measuring instruments are ...
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In the tunneling effect a particle with energy $E_1$ can pass through a thin barrier of height $V_0$ even if $E_1<V_0$. Since the wave function inside the barrier is not zero, then it is possible ...
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I am a high school teacher and in the coming year, I will introduce quantum mechanics to my AP physics course (I'm not actually in the US school system, but high school and AP physics are the closest ...
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If the wave function collapse is true then what in the early Universe observed things to create all of the different particles?
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In this article (https://physics.iitm.ac.in/~dawood/resources/pedagogical-articles/GRFessay_Kothawala_2013.pdf) in the abstract, it is said that Spacetime curvature will generically perturb the ...
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Can we say that the wave functions in a cup of tea, a blanket, a stool, and other surrounding objects, are collapsed due to the constant interaction of these objects with photons and other radiation?
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Very simple question, and I think it doesn't have an answer since CI is inherently incomplete. But when a particle is collapsed after being measured, what happens then? Does it remain a particle ...
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I'm particularly concerned with the conceptual consequences of this postulate, which I never quite pondered enough. In quantum mechanics, wave function collapse, also called reduction of the state ...
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I'm wondering if a similar scenario has already been proposed, or if this one is somehow valid. I'm a complete layman so be patient.My reasoning goes like this: is the collapse of the wave function a ...
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For a multi-particle system, superposition is in some sense equivalent to entanglement; with the Dirac field being treated as classical under second quantization, for example, we could at least argue ...
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