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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Weak measurements, non-demolition measurements and interaction-free measurements vs. wave function collapse [closed]
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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Another Entanglement Question - Can you tell if the wave function of an entangled particle is collapsed?
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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How do I calculate the probability distribution of momentum assuming that my instrument has a small spatial extension?
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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Does measuring a quantum object collapse the wave function even if the particle is not found in the position where it was measured?
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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Are there any theoretical reasons why we cannot measure the position of a particle with zero error?
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, to find a particle inside the barrier must I necessarily supply energy to the particle?
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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What experiments have been done which demonstrate that immediately after measurement, the collapsed state evolves unitarily again?
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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The collapse of the wave function in the early universe
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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Is curved spacetime related to entropy and/or quantum decoherence?
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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Are the wave-functions in surrounding objects collapsed?
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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What does the Copenhagen Interpretation say about after a collapse?
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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On the wave function collapse
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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Quantum collapse: our invention? [closed]
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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Is it possible that a macroscopic object tends to a separable state without the need for objective collapse?
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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Why are measurements considered irreversible?
In quantum mechanics, every interaction is described by a unitary Hamiltonian operator. We expect that a measurement is no different from any other interaction, yet in the standard way of treating QM ...
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How is Zig-zag Motion Observable in Quantum Mechanics Given Wave Function Collapse?
I'm puzzled by a concept I read about in a physics text concerning quantum measurement. The text describes the potential to observe a "zig-zag" motion if one could capture images of an ...
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Is spontaneous symmetry breaking possible without wave function collapse?
This is just a basic question to check my understanding (as a non-physicist).
An example to explain spontaneous symmetry breaking is given as follows: There is a particle that lies on the top of a ...
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Was Einstein "spooky action at a distance" about entanglement or about wave function collapse?
I've been watching Sabine's videos and this is my understanding:
There is no "spooky action at a distance" based simply on entanglement. Entanglement is a correlation. There is no ...
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In entanglement, does the measurement of one particle collapse the joint wave function or not?
I’m having trouble understanding what exactly happens when one makes a measurement on one particle, especially since I am seeing conflicting information on here, on Wikipedia, and from other sources.
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Finding literature with quantum tomography during a measurement to "see" the wave function collapse
I was at a journal club some time around 2020 where we discussed a paper that I am trying to find again. The claim was that it had experimentally shown that wave function collapse was not "...
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Relationship of the do-operator in do calculus and the notion of the collapse of wave a function
I stumbled over the "do calculus" in causal modeling https://arxiv.org/abs/1210.4852
and the do-operator which is defined in this post https://stats.stackexchange.com/a/643333/298651 The do-...
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Is there a limit to the number of observers to a wireless broadcast due to quantum mechanics?
My question seems obvious but nobody is talking about it. The way I understand it, an electromagnetic wave collapses to a particle when observed. This goes for electrons and photons but I imagine the ...
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What will be wave function after application of operator?
In the mathematical treatment of quantum mechanics, we have a wave function ($ψ$) that helps us to know the different information (like position, velocity, energy, etc.). To measure such a quantity we ...
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Is the collapse of the wavefunction relativistic?
If a stationary observer, 'A', observes the collapse of a wavefunction, does an observer, 'B', traveling at relativistic speed observe a different collapse of the same wavefunction?
What do all the ...
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Would quantum superposition stop if we observe the particle in the case of photosynthesis?
I started looking up more into quantum biology from photosynthesis to genetics mutation and how they are explained by quantum properties. my question is about the case of photosynthesis: quantum ...
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Collapse of Quantum State and Coefficients
I have found the following exercise in one of my problem sheets:
Suppose we have an observable $Q$ and its corresponding operator $\hat{Q}$ has three eigenfunctions $\varphi_1, \varphi_2, \varphi_3$ ...
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Measurement values affects probabilities in QM?
Consider a non-degenerate operator $\Omega$ with discrete eigenvalues $\omega_i$, where $i=1,2,3,...$. We can write $\Omega = \sum_i \omega_i~|\omega_i\rangle \langle \omega_i|$, where $|\omega_i\...
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Does a quantum measurement change the state in the past? [closed]
Consider the following very basic quantum mechanics experiment.
At time $t_0$, a system $S$ is in superposition of two orthogonal states $|A\rangle$ and $|B\rangle$, which we could describe by $\frac{...
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Shouldn't any measurement cause all wavefunctions to collapse?
Given the fact that every wavefunction exists everywhere in space, shouldn't a measurement at any location cause all wave functions to collapse since a measurement at any point measures all ...
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Doesn't the Copenhagen Interpretation violate the Second Law of Thermodynamics? [closed]
It feels like the transition from a sea of probability of a droplet of precision (or wave, depending what you're looking for) would be a loss of entropy, if so wouldn't this violate the Second Law? Or ...
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Can the collapse of the wave function be modelled as a quantum system on its own?
Imagine I have an observer $\mathcal O$, a quantum system $\mathcal S$ with Hilbert space $V_{\mathcal S}$, a Hamiltonian $H$, a self-adjoint operator $A$ acting on $V_{\mathcal S}$. The system is in ...
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Do objective collapse equations actually collapse the state?
Why are objective collapse theories stated to collapse the state from a superposition to a single eigenstate (corresponding to the measured eigenvalue)? For this discussion, we are focusing on the ...
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Quantum Collapse during the Measurement of the spectrum of hydrogen [closed]
We have hydrogen inside a tube, and we induce a voltage on it; a current passes through it and light is emitted. The frequencies of light correspond to the differences of the eigenvalues of the energy ...
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Gravity cause wavefunction collapse? (Roger penrose) [closed]
Roger Penrose suggested that gravity might play a role in the collapse of the wave function (which describes a system as a superposition of multiple values of Position, momentum etc.). According to ...
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FTL communication setup. Why wouldn't this work?
The setup is similar to quantum eraser experiments (see below). The laser pulses at regular intervals to send bunches of photons. They get split in half as entangled particles. One beam is sent 1 ...
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Double slit experiment with detector and experimenter
In the double slit experiment we have particles which travel through two slits and then hit a final wall/detector.
We can perform the experiment with or without an extra detector at the slits which ...
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Is wave function measurable?
I apologize for the length of this naive question. I am not sure it is appropriate for this community.
Is wave function measurable?
This is really a question in Atomic and Molecular Optics.
I hear ...
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Is the superposition of a particle before the collapse of the wave function a relative effect?
From the perspective of an electron in the double slit experiment, does the "rest of the universe" that it is disconnected from behave in the same manner as the electron does in our view? As ...
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How can a system be in superposition when there’s a force associated with it?
Not sure what the best way to word the title would be but I’ll explain further: suppose we’re talking about the double slit experiment. As the electron moves its electric field changes, which exerts a ...
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Wave functions of valence and conduction electron
I read that the standard depiction of covalent bonding is misleading. It gives the impression that the valence electron exists at that bond site. But really it exists as a wave throughout the crystal. ...
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What happens to the wave function after it collapses?
If a quantum particle is described by a certain wave function and we express it as superposition of for example its possibles energy states, after we measure it the wave function collapses and we ...
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Do the results of the Elitzur-Vaidman quantum bomb tester experiment imply that counterfactual events affect what is observed?
Assuming that light travels as photons that can interfere with themselves while also only being detected as specific localized points, the results of the Elitzur-Vaidman quantum bomb tester experiment ...
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Does collapse in different basis change probabilities differently?
Consider two quantum systems, with two associated Hilbert spaces $H_1, H_2$ and corresponding algebra of observables. Consider an entangled joint state of the two systems. In general it will be ...
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Physicality of post-measurement description of a state based on information of measurement outcomes
Say, we find two exact systems in a pure state. When Alice does von Neumann measurement on it, the state collapse to a pure state because Alice knows the measurement outcomes. In this case, we have $\...
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Is signal photon independent of idler photon in Delayed Choice Quantum Eraser?
--Diagram from Wikipedia of the experiment of Kim et al. (1999)
Original research paper: A Delayed Choice Quantum Eraser
I want to know whether the landing position of the signal photon (photon that ...
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In the double slit experiment, when emitting one photon at a time, why don't all of them travel the same path?
If we fire one photon at a time, why don't all of the photons hit the barrier exactly in between the two slits? How come each photon goes in different directions? (some go through top slit, some go ...
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Copenhagen Interpretation vs Quantum Decoherence? [closed]
I'm learning about Quantum Mechanics, and have a question about the Copenhagen Interpretation. It states that the act of observation collapses the wave function. It seems many people take this to ...
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What happen to the electromagnetic waves when a photon's "wave function" collapses?
We interpret the electron's wave function as a probabilistic wave function. During a measurement, it has the probability to collapse to any of the eigenstates of the measurement operator based on the ...
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Does the wave function collapse cause a high probability current?
If you perform a measurement the wavefunction collapses to a certain position. Does this mean there is a very high probability current to that position? Comparable to an strong electrical current ...
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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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