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Questions tagged [quantum-interpretations]

This tag is for questions relating to what, if anything, the quantum mechanical formalism and experimental results say about the way the world works.

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Spooky-action-at-distance, why it was claimed by Einstein?

If I understand "popular quantum mechanics" right, there is no faster-than-light communication via two entangled particles, because changing one of the particles (with the purpose to transfer a signal ...
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4answers
490 views

Is the wavefunction a real physical wave or only a mathematical abstraction? [closed]

Does interaction with physical slits in a double slit experiment indicate that the wavefunction is a real physical wave, as opposed to a mathematical abstraction? This question pertains to the psi ...
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1answer
97 views

What research (if any) is being done with regard to a hidden variable theory of quantum mechanics?

From Bell’s theorem and the Kochen-Specker theorem we know that any hidden variable model hoping to reproduce the predictions of quantum mechanics must be both non-local and contextual. What model ...
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1answer
241 views

Causality according to Dirac

Dirac writes in page number 4 of his "Principles of Quantum Mechanics": It is usually assumed that, by being careful, we may cut down the disturbance accompanying our observation to any desired ...
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1answer
478 views

What is an observer in QFT?

In non-relativistic quantum mechanics, an observer can be roughly describe as a system with wavefunction $\vert \psi^O \rangle$ which, upon interaction with another system $\vert \psi^S\rangle$ (in ...
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1answer
414 views

Why does entanglement not imply hidden variables?

By the causal symmetry of spacelike-seperated events, the statement "measurement of particle 1 causes subsequent collapse for particle 2" is equivalent to "measurement of particle 2 causes subsequent ...
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1answer
79 views

Meaning of contextuality

I'm trying to understand what contextuality means in quantum mechanics (-> Kochen-Specker theorem). Can someone describe '(non-)contextuality' in a mathematical way? Wikipedia says something like 'the ...
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1answer
107 views

Understanding the Mathematical Formalisms of Everetts MWI

Link to article: http://jamesowenweatherall.com/SCPPRG/EverettHugh1957PhDThesis_BarrettComments.pdf I'm writing an essay on Everettian MWI and its incompatibility with Born Rule probabilities. I ...
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5answers
887 views

Is it correct to say a quantum particle is in both “states” at the same time?

In popular media, and even in introductory books it is common to say that quantum objects are characterized by the non-intuitive notion of being in two or more eigenstates at "the same time". An ...
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1answer
221 views

Observation effect in double slit experiment [duplicate]

I have watched some of the lectures given by Brian Greene and Lawrence Krauss about the observation conundrum encountered during the double slit experiment. Can anybody answer me this question? Is ...
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1answer
132 views

MWI universal wave function question?

In MWI, there is only one wave function in the universe ( the universal wave function). So say if I detected a particle and its wave function decoheres, since the universal wave function never ...
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2answers
311 views

Position of collapse in von-Neumann chain

I have often seen the following claim (for instance on Wikipedia: https://en.wikipedia.org/wiki/Von_Neumann%E2%80%93Wigner_interpretation): In his 1932 book The Mathematical Foundations of Quantum ...
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1answer
274 views

Bell's theorem and how it solves the EPR paradox

Could someone explain to me how Bell's theorem solves the EPR paradox and 'spooky action at a distance'? From what I understand, when measuring a state, say spin up in the x direction, the wave ...
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3answers
245 views

Why does the universe need quantum superposition? [closed]

My question is not about the nature or reality of quantum superposition, superposition is a fact and no argue about that. My question is: What is the purpose of superposition and why does the ...
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2answers
706 views

Is there any physical significance to the orthonormality of states in a wave function?

In the infinite square well with bounds $0$ and $a$, the solutions to the time independent Schrodinger equation are: $$ \psi_n(x)=\sqrt{\dfrac{2}{a}}\sin{\left(\dfrac{n\pi}{a}x\right)} $$ One of the ...
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1answer
236 views

How did the von Neumann–Wigner interpretation got that name?

The von Neumann–Wigner interpretation says that consciousness causes collapse. Sometimes it is just called von Neumann interpretation. I don't believe that von Neumann ever said anything in that ...
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1answer
805 views

If Pilot Wave Theory is non-local, how does the pilot wave change over time?

My understanding is that Bohmian Mechanics (pilot wave theory) is non-local, meaning that effects propagate faster than light. Are these effects in fact instantaneous in that model? How would an ...
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0answers
40 views

Does quantum mechanics conserve information after a measurement? [duplicate]

I understand that QM without observers is unitary and conserves information. My problem starts when there is a measurement. It is my understanding that the measurement problem has not been adequately ...
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0answers
133 views

Does the Copenhagen interpretation reject probabilistic causation or does it merely reject deterministic causation?

Does the Copenhagen interpretation of quantum mechanics reject probabilistic causation or does it merely reject deterministic causation? I read that the Copenhagen interpretation rejects causation, ...
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1answer
161 views

Is there a difference between observation and entanglement?

I have very basic knowledge about quantum mechanic. I started wondering if there is any difference theoretically between observation and entanglement between subject and object. I.e. if we simplify ...
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1answer
285 views

Are particles really in a superposition before you observe the particle [closed]

So if I understood correctly, Schrodinger's Cat is a thought experiment that puts a cat inside a box, and there's a mechanism that kills the cat with 50% probability based on a quantum process. The ...
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1answer
88 views

Since photons do not experience time (nor distance in that case), why did Einstein think it was “spooky action at a distance”? [closed]

A photon travels at c, so it experiences no time or distance. I imagine from the photon's perspective, it's rather just like a simple dot on some kind of 4D manifold. So it begs the question of why ...
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1answer
92 views

How does the Copenhagen interpretation support the Pauli-principle?

In QM the Copenhagen interpretation states that there are behind the probalities no real values like spin-state. Now in the Pauli-principle electrons can't have both the same spin in the same 'orbit', ...
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0answers
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Is 'interpretation' in quantum mechanics the same as 'interpretation' in probability?

I heard all 'interpretations' of quantum mechanics give exactly the same answer to every measurement so they are all equally correct. Is that the same 'interpretations' as in probability? Context: ...
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1answer
173 views

How does the many-worlds interpretation explain that humans see just one world?

when I first heard about the many-worlds interpretation it was in the "popular" version about the universe "splitting" on the random events meaning one copy of the observer would see one outcome, and ...
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3answers
303 views

Is the wavefunction unique to the observer?

I know this may be beating a dead-horse, but I'm still puzzled by this topic even after reading so many other related SE questions/answers and online articles. I will be using the Copenhagen ...
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2answers
92 views

Yet Another Double-Slit Question [closed]

I'm not a physics graduate, I studied the subject to high school level but don't 'know the math'. But I'm interested in philosophy of science, and have read a number of popular books on the topic (e.g....
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1answer
836 views

Is the Many Worlds Interpretation deterministic?

Is the Many Worlds Interpretation deterministic? Considering that you can determine all of the possible outcomes of a wavefunction (pretty much impossible but still), the only random thing that ...
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1answer
121 views

Does photon bunching mean two photons fall on the same detector in both effects?

In Hong-ou-Mandel interferometers, it means the two photons exit the same output port of the beamsplitter and fall on a single detector but in the case of the Hanbury Brown and Twiss effect, does ...
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1answer
1k views

Decoherence. Does it solve the measurement problem? Is it discontinuous? When does it occur?

I am trying to better understand the current scientific consensus (to the extent that such a thing exists) on the interpretation of quantum physics. I understand that this is still very much an active ...
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1answer
249 views

Why parallel worlds in MWI do not interact with each other?

The quantum-mechanical " Schrödinger's cat " theorem according to the many-worlds interpretation (MWI). In this interpretation, every event is a branch point; the cat is both alive and dead, even ...
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2answers
208 views

How can you be a realist and not posit an ontological model?

I have a specific technical question about how to formalize models for quantum interpretations. My question arises from the talk Why I am not a psi-ontologist, by Rob Spekkens at the Perimter ...
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1answer
143 views

Is QED without measurement a local hidden variable theory?

An interesting thought experiment would be to create a large quantum wave-function describing both a pair of electrons with entangled spins and the equipment needed to measure the electrons' spins. In ...
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2answers
180 views

Does many world interpretation of quantum mechanics also apply to macroscopic objects?

Since macroscopic objects have more particle like nature and they are always being observed (interact) with their surrounding, does MWI also applies here and if yes then what is its significance. Is ...
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1answer
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What are the differences between a $\psi$-epistemic ontological model and a $\psi$-ontic model of quantum mechanics, exactly?

I am confused about the differences between a $\psi$-epistemic ontological model of quantum mechanics and a $\psi$-ontic one. The way I understand it, a $\psi$-epistemic model says that every quantum ...
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2answers
52 views

Necessity of World splitting in Many-World-Formalism

I am reading descriptions about many world formalism, where the idea of "one wavefunction for the whole universe" makes sense to me. Everything goes so well until I read the "world splitting part": I ...
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12answers
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Does the Many Worlds interpretation of quantum mechanics necessarily imply every world exist?

I know the Many Worlds interpretation is controversial among physicists, but it's been a pop culture hit nonetheless. I frequently see people making statements like, "Well in another universe I'm a ...
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0answers
176 views

Why is the wavefunction not a hidden variable?

Consider the following standard case of an entanglement experiment: We prepared two electrons A and B with states $$\lvert A\rangle=a_1\lvert \uparrow\rangle+a_2\lvert \downarrow\rangle$$ $$\lvert B\...
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2answers
637 views

How do we know certain aspects of QM are unknowable?

In a course on modern physics we are beginning to get into probability amplitudes and the inherent unknown in some things, say the position of an electron in an orbital. How do we know that these ...
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2answers
605 views

How does QFT account for localization (into a finite volume of space), in practice?

In Quantum Field Theory there is until yet no agreement (as far as I know) on the issue of localization of particles. When one talks about a 'particle' in QFT, one usually means a single-particle ...
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3answers
158 views

Is the Schroedinger picture outside the contemporary maintstream?

By the Schroedinger picture, I mean the notion that atoms exist in a superposition of states, as opposed to the Copenhagen picture, which I understand to mean that in a system of atoms, all the atoms ...
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1answer
46 views

What happens that doesn't allow our measurement?

Suppose pair production results in an electron and positron pair in an entangled system. One person (A) measures the electron and another person (B) measures the positron. Another property of this ...
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3answers
466 views

Is the energy of single photon defined by uncertainty relation? What is the pulse duration of sigle photon beam?

Coherent sources can have ultra short pulse durations provided there is at least one photon in frequency that span broad bandwidth (and are coherent)? Does that mean that the pulse duration is ...
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3answers
202 views

Does the Copenhagen interpretation say that a tree only has definite mass after I look at it?

Assume that the Copenhagen interpretation holds. Imagine a Universe, a nearly identical copy of our Universe, that contains only our Earth and me (i.e., I'm the lone conscious being and the lone self-...
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1answer
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Pilot waves and quantum eraser; pilot wave simulation

I recently watched this video about the quantum eraser experiment on PBS spacetime: Link. Has an experiment like the quantum eraser been tried with the pilot wave theory, ie bouncing droplet ...
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0answers
77 views

single Observer iterpretation, experiment design

I am thinking of an interpretation of QM in which there is a single Observer (O). That is, its mind's history is marking a special path on the many-world graph, which we identify with reality. This ...
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0answers
185 views

Quantum Mechanics Vs nonlocal causality

There is an article in Physics world.com dated August 18, 2016, titled "Quantum Mechanics Trumps Nonlocal Causality. The author of the article Philip Ball quotes one of the experimenters ( i.e. ...
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4answers
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Outcome of Mach-Zehnder interferometer experiment

I am reading David Deutsch's The Beginning of Infinity. In chapter 11, he explains the basics of quantum theory and gives evidence for the many worlds (Everett) interpretation. The argument uses a ...
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2answers
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Can the Copenhagen interpretation and the many-worlds theory be somehow reconciled? [closed]

Is it possible that, at the moment of observation, a timeline is created where an object is in a state which contrasts its state in the current timeline? Using Schrodinger's cat as an example, let's ...
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1answer
60 views

What happens with QM particle at constant velocity? [closed]

In QM particles have wavefunctions that disperse quite fast. The FWHM for gaussian wavepacket increases in time as $\Delta x(t)= \Delta x_0\sqrt{1+(t/\tau)^2} $, $\tau=2m(\Delta x_0)^2/\hbar$ What ...