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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Books on Quantum Measurement

I have been trying to understand clearly the concept of non locality, hidden variables, quantum measurement etc through research papers. I also read Quantum Theory and measurment by Wheeler and Zurek ...
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299 views

EPR Paradox resolution: the spin is fixed at creation but its measurement isn't?

The Wikipedia article on the EPR paradox uses the example of an electron and positron created from a common source, each moving in an opposite direction to the other. Detector A is used to measure the ...
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1answer
139 views

Atom in a box and collapse of the wave-function

Suppose I have an atom trapped in an optically transparent box. I'm assuming the atom is bouncing off of the walls and not bonding, i.e. the center of mass of the atom experiences a square well. Now ...
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1answer
215 views

Entanglement distillation - Interpreting a protocol

I have a general question regarding the interpretation of a enganglement distillation protocol. In general you have a set of entanglet qubit pairs in a Werner-state. Point of matter of this is that I ...
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234 views

Can the Lorentz force stabilize the Hydrogen atom?

I've recently been working on relative equilibria for some systems of particles. (ie. studying equilibrium solutions in a rotating frame. Saturn's rings for example.) This has evolved into some ...
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1answer
97 views

Is the time of collapse of the wave function empirical?

Is the time of the collapse of the wave function empirical? Suppose there is a very long von Neumann chain of observations of a quantum system. Suppose also practically irreversible decoherence ...
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1answer
178 views

The System and the Measuring Gadget

In Quantum Mechanics the value of an observable results from the interaction between the "system" with the "Measuring gadget". But when the experimenter[or the technologist concerned] is ...
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1answer
416 views

Worlds branching or diverging in Many-Worlds Interpretation? [closed]

In recent years there seems to have been a growing discussion surrounding MWI's ontology. In the 2010 volume "Many Worlds?", Simon Saunders has a chapter dedicated to discussing whether the worlds in ...
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143 views

How do you properly analyze decoherence when the system-environment interaction is strong?

The standard decoherence analyses work something like this. Split the universe into a system and its environment, and split the Hamiltonian as the sum of the system Hamiltonian, environment ...
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68 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 ...
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42 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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29 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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2answers
212 views

Many-world interpretation: simple physics explanation? [closed]

We went a little off topic in physics class today and my teacher was explaining how quantum physics explains the idea of parallel universes. She believes in a idea called many world interpretation ...
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2answers
87 views

Light interference single particle 4 slits experiment - what are interpretations apart from many-worlds interpretation?

Someone knowledgeable about physics advised me to read a book "David Deutsch: The Fabric of Reality, 1997". The book gives experiment like two-slit one, difference is that 2-slits compared to 4-slits ...
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0answers
58 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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110 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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25 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 ...
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1answer
123 views

Immortality within the multiple worlds interpretation of quantum mechanics [closed]

I understand the multiple worlds interpretation of quantum mechanics as follows: Any time an event happens, all of the possible outcomes take place ("split the universe") If I then think about a ...
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2answers
128 views

multiverse fabric of reality

Source-"fabric of reality"- author d. deutsch - his contention, as I understand it, is that quantum interference is caused by "almost, but not identical quite quantum entities" , e.g. electrons, from ...
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24 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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58 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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40 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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91 views

I don't get the concept of “God plays with dice” - In what scenario is it proven that he does? [duplicate]

Does God Play With Dice? by Stephen Hawking I am no physicists, but I don't get the concept of God playing with dice. Logic shows me that the entire universe is calculated very precisely according ...
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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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114 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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92 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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114 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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231 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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56 views

Interpretation of theoretical Schrodinger's cat experiment [duplicate]

I do appreciate how to interpret the famous theoretical experiment of Schrodinger's cat experiment in the following situation: A Lab has a closed box with a dead or live cat and and a person who ...
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3answers
228 views

According to wave function collapse you only have one outcome, so what happens to the other superpositions?

If the superpositions of a wave function are not needed because only one of the superpositions is allowed, what happens to the eigenvalues of the "null" superpositions? Is the energy transferred ...
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59 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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348 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 ...
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1answer
83 views

In the many worlds interpretation of q.m. what makes a superposition af states split in two sepearate ones?

I was wondering, what agent makes a superposition of, let´s say, the two spins of an electron, máke them split into two separate ones (up and down). And is this not in contradiction to the law of ...
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1answer
94 views

Are The Quantum Assumptions of MBT Theory Correct?

I've become very interested in Tom Campbell's MBT Theory (Plenty of YouTube videos). I can't explain it all here because it takes a book (The one he's written). It's based on the virtual reality ...
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2answers
2k views

If the moon is not there when no one is looking, how does the moon know how to stay in orbit between observations? [closed]

Quantum Copenhagenists will tell you if there is a stop sign, it only manifests itself by the act of observation. When no one is looking, there is nothing there. This is like the cognitive process of ...
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2answers
106 views

Do conservation laws contradict quantum mechanics? [on hold]

Take for example the double-slit experiment interpreted in the Copenhagen sense. The particle leaves as an object with mass, yet passes through the slits as a massless wave, only to collapse again as ...
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1answer
51 views

What is the difference and/or similarity between multiple universes in inflation and in quantumphysics? [duplicate]

Some theories propose that there are more universes. In one of them it is said that there are parallel universes, due to inflations after the big bang that created them. But in the two-slit ...
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1answer
243 views

How does this youtube video demonstrate quantum entanglement? [closed]

The following is an experiment that shows "spooky action at a distance" of quantum entanglement; that is, when we measure some properties of two entangled photons, we find that measuring property of ...
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1answer
135 views

In Quantum mechanics, what is realism? [closed]

Some interpretations of QM are realist and some are anti-realist. But, it is the idea that something exists before it is measured, correct?
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1answer
68 views

Probabilistic realism

On consideration of Bell's inequalities and this Why is quantum entanglement considered to be an active link between particles?. Either localism or realism has to be given up. Can't we have a ...
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1answer
76 views

Are there nonlinear models of quantum mechanics which forbid superluminal signaling?

What would a nonlinear model of quantum mechanics which forbids superluminal signaling look like? Of course, a nonlinear $\psi$-ontic theory with entangled states could have superluminal effects upon ...
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1answer
84 views

Does alternative reality theoretically prove? [closed]

Does Hugh Evert theory means Alternative-Reality (or in general, Parallel-Worlds) and Many-Worlds-Interpretation theoretically prove? Or are scientists have any progress to prove it?
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441 views

Consciousness and quantum mechanics [closed]

Quantum mechanics is very mysterious. Consciousness is often brought into play to explain quantum phenomena. Is this only a matter of convenience, or is consciousness inherent to interpreting quantum ...
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3answers
158 views

Has the double-slit experiment been performed with animals as the observers?

As the title says, has the double-slit experiment been performed with animals (not humans) as the observers? If yes, which animal was used and what was the result?
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1answer
86 views

Does the uncertainity principle actually attack determinism? [closed]

It's not really clear to me how does QM attacks determinism. It sure attacks computability, which is a component of newtonian, naive determinism, but it's often claimed to destroy determinism itself ...