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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Is frequency or Bayesian interpretation used in quantum mechanics?

In quantum mechanics, we discussed about probability. There are two kinds of interpretations: frequency and Bayesian. Which one is actually used in quantum mechanics? My impression is, it doesn't ...
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114 views

Free Will Theorem question

The Kochen-Specker Theorem says, if I understand it correctly, that the results of spin measurements cannot be predetermined independent of measurement. They get to this conclusion by describing 33 ...
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144 views

Is it possible to reproduce the energy spectrum of quantum chaos using classical cellular automata?

Is it possible to reproduce the energy spectrum of quantum chaos using classical cellular automata? It's hardly impressive to reproduce harmonic oscillators.
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86 views

Decoherence and interpretations

With quantum decoherence, are there still any "gaps" in our knowledge of quantum mechanics that hint (either in terms of the physics, philosophy, or otherwise) at the need for further interpretation? ...
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96 views

Are frequency and likelihood the same across the multiverse?

My probability text distinguishes between two interpretations of probability values: the frequency of occurrence "as percentage of success in a moderately large number of similar situations" (coin ...
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64 views

Are there any connections between James–Stein estimator and quantum mechanics?

Very nice statement from wiki: When three or more unrelated parameters are measured, their total MSE can be reduced by using a combined estimator such as the James–Stein estimator; whereas when ...
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422 views

Does the extended probability ensemble interpretation of quantum mechanics make any sense?

Gell-Mann and Hartle came up with the extended probability ensemble interpretation over here. Basically, they extended probability theory to include real numbers which may be negative or greater than ...
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68 views

Is there a video of a double-slit experiment using walking oil droplets (aka dotwaves)?

I've heard there have been experiments with walking droplets in a double-slit setup, and I've seen videos of many of the other quantum phenomenons walking droplets can emulate, but I can't find one of ...
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217 views

Testing Many-Worlds Interpretation (MWI) with a causality-violating configuration of “superluminal cables”

Suppose we managed to arrange a causality-violating transmission of data with hypothetical “superluminal cables” (SLC; see both links for respective descriptions) and expect, similarly to ideas ...
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199 views

Are universally valid possibilistic theories possible?

This is a spin-off of the following question: Are Thomas Breuer's subjective decoherence and Scott Aaronson's freebits with knightian freedom the same things in essence? Given that Thomas ...
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136 views

How can the pre-measurement be fulfilled?

In the decoherence program, the pre-measurement refers to the evolution in which the system and apparatus form a Schmidt state. In Maximilian Schlosshauer's review article(2005), I read "the linearity ...
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267 views

Uncertainty Principle and Bohmian mechanics

The Uncertainty Principle is a relationship between measurements of pairs of attributes, position and momentum, as well as energy and time. Perfect precision of one attribute's measurement leads to a ...
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57 views

Is it possible to detect subjective decoherence? If yes, how?

In his paper from 1994 Thomas Breuer describes a phenomenon of subjective decoherence (p. 43). I wonder whether it can be measured, and if yes, how. I also wonder whether it would allow to create an ...
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126 views

How to explain Tsirelson's inequality using extended probabilities?

How to explain Tsirelson's inequality using extended probabilities? Some people have tried explaining the Bell inequalities using extended probabilities. For instance, a pair of entangled photons ...
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65 views

Why not measure the velocity of a quantum particle by $\frac{\Delta \vec{x}}{\Delta t}$

Why is it not possible in quantum mechanics to measure the velocity (and thus momentum) of a particle just by two position and time measurements and get it approximately by $$ \vec{v} = \frac{\vec{x}...
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99 views

What is the justification for continuing to model space-time as a manifold in string theory?

Background The question I have arises from taking seriously the idea that, in a physical theory, one should first define all physical quantities via (thought) experiment. Justification and ...
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42 views

Mathematical formalism for the Many World's Interpretation of Quantum Mechanics

A short question: is there a mathematical formalism underlying the Many Worlds Interpretation, that is published in the literature, in much the same way, but on a presumably smaller scale, as String ...
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43 views

How can a spinor represent an “epistemic” state?

I have read a lot of stuff on the seemingly endless debate on ontology/epistemology of the quantum state $\psi$. But I always wonder: how can a spinor be considered epistemic when $\psi$ really ...
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56 views

Information loss from entanglement and cosmological horizons?

Suppose we have a qubit P in an unknown quantum state. Unknown as in we didn't prepare it, and don't know how it was prepared either. Without measuring the qubit in any way, we encode it into two ...
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60 views

Would it be possible to Loschmidt reverse Wigner's friend using future technology?

Would it be possible to Loschmidt reverse Wigner's friend using future technology? Why or why not? Can a human be isolated in a decoherence shielded box? Can we have fine control over every single ...
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86 views

Many Worlds or Infinite Worlds?

Looking at the latest paper to deal with the topic: where it purports to show that QM can be recovered from the interactions of a multitude of Newtonian worlds, we have the following statements: ...
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69 views

Is relational QM experimentally distinguishable from standard QM?

Some people advocate for relational quantum mechanics, which is an interpretation (or at least Wikipedia calls it an interpretation) of QM where quantum states are thought of as representing a ...
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128 views

Why are cosmic conspiracies considered undesirable in quantum interpretations?

Quantum interpretations like superdeterminism, nonlocal hidden variables, etc. are regularly dismissed by the vast majority of physicists because they require "cosmic conspiracies" which can ...
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106 views

What is a potential in De-Broglie-Bohm theory?

As I have so far understood, the De-Broglie-Bohm theory is based on two equations: The Schrödinger equation. The Guiding equation of the De-Broglie-Bohm theory. In the Schrödinger equation (as ...
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60 views

Is there any “fundamental” uncertainty to the timing of the Big Bang?

I wondered whether, under the probabilistic interpretations of QM, the timing of the Big Bang (or perhaps any other historical event) is fundamentally as uncertain as (or: like) other (e.g., future) ...
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95 views

What is the difference between Cramer and Vaidman?

Two very interesting new papers on arXiv last night by Lev Vaidman and friends lead me to ask about the differences between Cramer's transactional interpretation of quantum mechanics (TIQM) and the ...
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88 views

Hamiltonian matrix propertu

A professor made an statement to prove the variational theorem: Because the Hamiltonian (H operator of quantum physics) is diagonal in its own eigenfunction, the terms in $\left \langle \Phi _{m} \...
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194 views

Consistent histories and Bohm mechanics, many worlds in disguise?

This was posted on here in someone's Phys.SE answer: No, in the many worlds interpretation, every parallel universe is real, but in consistent histories, once you choose your projection operators, ...
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122 views

Bohmian Quantum Mechanics diffusion

About one year ago I attended a pretty interesting seminar of Nino Zanghì on the actual state of Bohmian mechanics. Now, during my undergraduate studies, I didn't have the possibility to take a class ...
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72 views

Can't many-worlds interpretation explain wavefunction collapse?

According to the many-worlds interpretation when universe splits in interaction, the observer in each universe measures corresponding pure state thus seeing collapse. Well, it may be an interpretation,...
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48 views

Interpretation of a case of the double square well

Consider a 'double square well' potential (where $E < 0$) defined as: $$V(x) :=\begin{cases} -V_0~~~~~~~~~~~~~\text{for }\frac{b}{2} < x < \frac{b}{2} + a \text{ and } -a - \frac{b}{2} < ...
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31 views

Statement of vector model of angular momentum in Eisberg and Resnick

While serving as a teaching assistant for a sophomore-level Quantum Physics course, I came across the following paragraph in Eisberg and Resnick regarding orbital angular momentum (section 7-8, page ...
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64 views

How does one intrepret probabilites in the many-worlds interpretation?

Let's say I flip a coin, and don't look. From the copenhagen interpretation, the state of the coin is: $\frac1{\sqrt2}(i|\text{heads} \rangle - |\text{tails}\rangle)$ If I observe the coin, there is ...
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59 views

A real 'two line' (non-interference pattern) when observed

I have seen many interference patterns from double slit experiments but I have never seen a real 'two line' pattern when observed. Does this actually exist or is it only a conclusion? if there is an ...
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113 views

Using the double slit experiment to prove or disprove the de Broglie-Bohm pilot wave theory

Probably a dumb question... If you have a double slit experiment with a second experiment (single or double slit) at 90 degrees intersecting the path of the first experiment, would the interference ...
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58 views

Can string theory and the Penrose interpretation coexist?

Is it possible for string theory to coexist with the Penrose interpretation of quantum mechanics? Does string theory require the many worlds interpretation?
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26 views

Can the rate of branching in the many worlds interpretation be influenced?

If I understand correctly, in the many worlds interpretation, worlds branch when irreversible interactions occur, and that these interactions occur on very low-levels. Since they occur on such low ...
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72 views

Interpretations of Quantum Mechanics and Locality

I have read these posts here: Why do people still talk about bohmian mechanics/hidden variables Disproof of Bell’s Theorem What combinations of realism, non-locality, and contextuality are ruled ...
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157 views

What does Bell's theorem rule out?

What exactly did Bell's theorem rule out? Did it rule out "locality", so we must give up and think of Copenhagen or maybe some realism theories (Bohmian for example)? ... That's how I understand Bell'...
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25 views

Does quantum complementarity inherently require ensembles?

If there are two complementary observables, $P$ and $Q$, it does superficially appear as if the only kind of empirical evidence we can get for complementarity has to come from statistical data from an ...
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61 views

finetuned quantum experiments by Murch lab, do any have dynamics outside of basic QM formalism/ axioms?

a series of very finetuned quantum experiments have been reported by the Murch lab eg in 2 articles in Nature & analysis there,[1][2][3] some leading to dramatic accounts in the media.[4] do ...
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42 views

In MWI, how to make sense of the nonuniqueness of decomposing mixed states into pure states?

It's well known that in quantum mechanics, a generic mixed state can be decomposed into pure states in infinitely many different ways. While this property is kind of understandable if quantum states ...
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100 views

Bell's inequality

For a project, I'm planning to study Bell's inequality, which as far as I can gather is taken to rule out hidden variable theories of QM. I'm looking for recommendations of decent sources which derive ...
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115 views

Test for Many Worlds Hypothesis

If one actually ran an experiment similar to the Schrodinger's cat thought experiment, and ran it enough times (with the same cat) to get the confidence interval good enough, could one say that ...
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27 views

Representation of a Signal and its evolution via Quantum System

I am a total beginner in the field of Quantum Mechanics. So, the question I am asking may be a silly one. So kindly give me possible answers or advice for modifications. Recently I am learning the ...
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94 views

Born rule and Feynman propagators

Let us assume that we want to describe the full process of photon emission by electron A and absorption by electron B. Therefore electron B must be on the forward lightcone of electron A. In the ...
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115 views

The status of unobservable quantum mechanical predictions

Orthodox quantum mechanics intrinsically requires an observer - since the only connection from the mathematical formalism to physical reality is through the measurement axiom (probability of observing ...
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233 views

Is the Copenhagen interpretation still valid?

"The secret lives of photons revealed" - physicsworld.com. It seems that this experiment violates the Copenhagen interpretation. Is it still valid? Can you please give me more insight on this ...
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61 views

Does the nonlocality of the preferred basis mean QM is nonlocal?

Take the Mach-Zehnder interferometer as an example. A photon passes through a beam splitter, is reflected off mirrors, and interferes with itself at another half-silvered mirror. No measurements or ...
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353 views

Hardy's Theorem

https://perimeterinstitute.ca/psi_portal/sites/perimeterinstitute.ca.psi_portal/files/hardyphysrevlett.68.2981.pdf Some researchers in Bohmian Mechanics have hoped to make the theory Lorentz ...