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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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13
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2answers
625 views

Are quantum decoherence and Everettian approaches to the measurement problem necessarily distinct?

As I understand it, there is a large contingent of physicists who believe that the measurement problem is "solved" by decoherence, without, for example, needing to postulate the existence of "many ...
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5answers
2k views

Why doesn't Many-Worlds interpretation talk about many worlds?

I was reading this interpretation from this site, where these lines are noteworthy enough to talk for the fact that this interpretation doesn't actually talk about many-worlds: These are the "many ...
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6answers
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Connection between quantum physics and consciousness

Can someone explain the quantum physics-consciousness connection? In the double slit or quantum eraser experiments, the system behaves as a whole, with some apparent time independent traits. Invoking ...
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3answers
2k views

What are specific arguments against the ensemble interpretation (as promoted by L. Ballentine)?

Leslie Ballentine develops in QM: A Modern Development an interpretation based on the ensemble interpretation, and responds to most criticisms. My question: what criticisms still exist against this ...
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4answers
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Assumptions in Bell's Theorem

It is often Stated that Bell's Theorem is equivalent to the statement: No theory of Local Hidden Variables can reproduce all of the predictions of quantum mechanics. I see nowhere in Bell's Theorem ...
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7answers
999 views

Why Quantum Mechanics as a non-fundamental effective theory?

My question: What (physical or mathematical) reasons (not philosophical) do some physicists ('t Hooft, Penrose, Smolin,...) argue/have in order to think that Quantum Mechanics could be substituted by ...
11
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3answers
737 views

Is it possible to define a “it went through two slits” observable?

This concerns the famous two-slit experiment. Electrons or photons or your favorite particle, doesn't matter. As we all know, the attempt to detect which slit the quanta pass through leads to loss ...
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4answers
3k views

What defines which universe I will end up in? [closed]

Following this question about the Many Worlds Interpretation of QM in which MW is stated to be deterministic: What "chooses" which universe I will be in, i.e., which outcome I will see? I actually ...
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3answers
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Couder-Fort Oil Bath Experiments and Quantum Entanglement Phenomena

The oil bath experiments of Couder and Fort have been able to reproduce various "pilot wave like" quantum behavior on a macroscopic scale. Particularly striking is the fact that the double-slit ...
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8answers
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Is the quantum analog of a probability distribution the wave function or the density matrix?

Classically, probability distributions are nonnegative real measures over the space of all possible outcomes which add up to 1. What they mean is open to debate between Bayesians, frequentists and ...
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3answers
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What is the physical interpretation of the density matrix in a double continuous basis $|\alpha\rangle$, $|\beta\rangle$?

(a) Any textbook gives the interpretation of the density matrix in a single continuous basis $|\alpha\rangle$: The diagonal elements $\rho(\alpha, \alpha) = \langle \alpha |\hat{\rho}| \alpha \...
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1answer
449 views

Does Hardy's paradox represent a proof against Bohm's interpretation of the quantum mechanics?

This is a thought-experiment, see "Quantum Mechanics, Local Realistic Theories, and Lorentz-Invariant Realistic Theories", Phys. Rev. Lett., Vol. 68, No. 20, page 2981, year 1992, that rules out local ...
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1answer
882 views

Is a weak measurement the same as an unsharp measurement or POVM?

This is prompted by the strong claims made in Science 332, 1170 (2011) to have observed trajectories of photons, "something all of our textbooks and professors had always told us was impossible". I'm ...
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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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2answers
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Shor's algorithm and Bohmian Mechanics

Do quantum computer's tell us anything about the foundations of quantum theory? In particular Shor argued in the famous thread by 't Hooft Why do people categorically dismiss some simple quantum ...
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3answers
3k views

Determinism, classical probabilities, and/or quantum mechanics?

[I]f you want a universe with certain very generic properties, you seem forced to one of three choices: (1) determinism, (2) classical probabilities, or (3) quantum mechanics. [My emphasis.] Scott ...
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3answers
919 views

Could quantum mechanics work without the Born rule?

Slightly inspired by this question about the historical origins of the Born rule, I wondered whether quantum mechanics could still work without the Born rule. I realize it's one of the most ...
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3answers
1k views

Bohmian loophole in PBR-like theorems

I'm reviving and expanding this question, because of the new paper today, by Aaronson et al. The more general question is: How does quantum-potential Bohmian mechanics relate to no-go theorems for ...
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4answers
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Quantum Physics and the Law of Large Numbers

On page 1 of this recent paper by Bousso and Susskind we read. This question is not about philosophy. Without a precise form of decoherence, one cannot claim that anything really "happened", ...
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4answers
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How do we know particles exist? Aren't they just waves?

In the book "A Briefer History of Time" Stephen Hawking wrote: The unpredictable, random element comes in only when we try to interpret the wave in terms of the positions and velocities of ...
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5answers
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Why is the Copenhagen interpretation of quantum physics the most widely accepted one?

I've been digging a lot into quantum physics in the last few weeks. I didn't care much about the maths, just about what empirically happens to get a conceptual idea about quantum phenomena. The most ...
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3answers
687 views

Can someone clarify whether the recent experiment closing all remaining loopholes to Bell's Theorem really shut the door on local realism for good?

I saw this recent article on Phys.org that purports to close all remaining loopholes that previous experiments on violations of Bell's inequality left open. My question is, does this really close the ...
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5answers
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In the oil droplet experiments that suggest de Broglie’s pilot wave theory might be accurate, what does the fluid surface correspond to?

As a particle travels to a screen, it is traveling through 3-dimensional space. In the oil droplet experiment, there are only two dimensions of any importance—the droplet merely moves along the ...
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2answers
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What is the meaning of Wheeler's delayed choice experiment?

Wheeler's delayed choice experiment is a variant of the classic double slit experiment for photons in which the detecting screen may or may not be removed after the photons had passed through the ...
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3answers
634 views

How do probabilities emerge in the many-worlds interpretation?

My understanding is that at each quantized unit of time that a split occurs, every possible recombination of particles occurs in the 'objective' universe. If this is the case, what relevance to ...
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3answers
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What happens after the collapse of a wavefunction?

If I have a quantum system which I prepare in a certain state, this state then evolves unitarily via a Hamiltonian. Suppose an observer provokes a collapse of the wave function by a certain ...
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3answers
693 views

Many-worlds interpretation vs 'just' randomness?

I have this question about MWI I always wanted to ask but never dared to! It could be that I just don't know enough physics to understand the answer, or the question! Anyway, here goes: What is it ...
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3answers
467 views

Does processing for a quantum computer take place in other universes?

Apologies in advance if my question seems misinformed. I am a software developer, and neither quantum mechanics nor physics are my specialties. From http://physics.about.com/od/quantumphysics/f/...
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1answer
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EPR paradox and uncertainty principle

In Wikipedia article EPR paradox, The original paper purports to describe what must happen to "two systems I and II, which we permit to interact ...", and, after some time, "we suppose that there ...
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5answers
316 views

A non-metaphysical interpretation of measurement in quantum mechanics

In quantum mechanics, measurement plays a fundamental role and to me, its role is usually described in a rather odd way. The Copenhagen interpretation states thus When that device makes a ...
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3answers
480 views

Is the Copenhagen interpretation merely an approximation to quantum mechanics?

So, I'm reading Max Tegmark's Our Mathematical Universe (Knopf edition, p. 229). He's discussing Everett/MWI for a bit and I'm not really paying attention and then I wake up to this: [I]t's time to ...
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3answers
688 views

What is the physical meaning of weak expectation values?

In the two-state formalism of Yakir Aharonov, the weak expectation value of an operator $A$ is $\frac{\langle \chi | A | \psi \rangle}{\langle \chi | \psi \rangle}$. This can have bizarre properties. ...
10
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1answer
390 views

Can observers be particles?

Generally Quantum mechanics divides a system what is to be observed and an observer. This is generally taken to be some human being. But why restrict it to such? Why not a particle? Is there a good ...
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2answers
210 views

What is the physical meaning of the sum of two non-commuting observables?

Scenario: ${\mathcal A}$ and ${\mathcal B}$ are two observables. Mathematically we model them by two Hermitian operators $A\colon H \to H$ and $B\colon H \to H$ on a separable Hilbert space. ...
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1answer
4k views

Box normalization

Whenever we study free fields, the solutions of these fields (or particles, whatever feels most comfortable) are always given by plane waves. The dispersion-relation $\omega=\omega(k)$ will of course ...
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3answers
1k views

Does Dirac's argument against classical mechanics stand in contradiction to Bohm's theory?

In his book on Quantum Mechanics, P.A.M. Dirac talks about the stability of the atom as a means of demonstrating the need for quantum mechanics. He writes: The necessity for a departure from ...
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5answers
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Quantum Wave Mechanics

I am studying QM-I these days. Now, I just think of the wave function as just a mathematical function that defines the state of the particle at an instant and from it you can extract various ...
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6answers
2k views

Which physically acceptable quantum interpretations do not require the existence of any observer at all?

Some interpretations of quantum mechanics — like the Copenhagen interpretation in particular — require the existence of an observer. The role of the observer is a bit mysterious. After all,...
7
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2answers
256 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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3answers
2k views

Is contextuality required in quantum mechanics?

I still don't really understand what contextuality means in reference to quantum mechanics. If someone could give a clear definition that would be great. It sounds like it means you can't always ...
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2answers
606 views

The Pusey, Barrett and Rudolph (PBR) theorem and “shut up and calculate”

I was looking around for a competent, recent, persuasive presentation of the "shut up and calculate" philosophy regarding interpretations of quantum mechanics, and google led me to Fuchs and Peres, "...
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2answers
336 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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3answers
538 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 ...
3
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4answers
643 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 ...
3
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3answers
460 views

How does the Physics work for the Quantum Suicide thought experiment?

On page 5 of this paper written by Max Tegmark, Tegmark discusses a thought experiment called 'Quantum Suicide'. As far as I understand it, this experiment was created to show the experimental ...
3
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2answers
332 views

Unitarity and measurement

I used to believe that the wavefunction collapse came from the interaction of the system we want to measure {S} with the measurement apparatus {M} : {S} undergoing a non unitary transformation, but {S+...
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1answer
280 views

Why should multiple versions of a weak measurement preclude it from being a measurement of intrinsic properties of some system

I've been trying to understand Stephen Parrott's criticisms of weak measurement, outlined most concisely here: http://arxiv.org/abs/0909.0295 One of his major criticisms is that weak measurement is ...
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2answers
968 views

Entropy before and after collapse of the wavefunction and interpretation?

Seems like it might be pretty rudimentary but I want to see if my thinking is on the right track as well as what the result means. The question is, is the entropy of the collapse of a wavefunction or ...
2
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1answer
1k views

Can silicon droplets bouncing on a vibrating surface be a model for Quantum Mechanics? [duplicate]

In this video on youtube it is claimed that silicon droplets bouncing on a vibrating surface show behaviour in analogy to particle/wave duality in Quantum Mechanics. Is this true? Did they really ...
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6answers
405 views

Meaning of probability in a multiverse/a many-world interpretation?

Consider me tossing a coin and I got tail as a result on observing it. Then, what would be the result of the 'parallel me' in another universe? If the 'parallel me' gets head as a result then, ...