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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92 views

If Copenhagen interpretation is true, why can't a blind man throw a ball through a wall?

If it is true that particles are in different potential locations until an observer comes along and collapses the wave function, then how can a blind man throw a ball and hit a wall if the particles ...
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4answers
182 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, ...
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1answer
102 views

Non-locality and Bell's theory

Non-Locality – (just ) one more question? I have read comments that Bell’s theory proves quantum mechanics is non-local, and also comments that it does not. I have read a comment by a very eminent ...
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1answer
136 views

Does quantum reversibility require many worlds?

The source S sends a photon into the beam splitter below. There is a 50% chance that it will be detected at A and a 50% chance it will be detected at B. ...
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2answers
206 views

What are hidden variables exactly?

What are hidden variables in quantum mechanics? I am aware there are many types but what exactly do they mean or even "do" exactly? Do they mean that the quantum indeterminacy becomes hidden but ...
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2answers
596 views

EPR-type experiments and faster-than-light communication using interference effects as signaling mechanism

I understand that faster-than-light communication is impossible when making single measurements, because the outcome of each measurement is random. However, shouldn't measurement on one side collapse ...
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1answer
154 views

Who are “we”, and what counts as a “question” in consistent histories?

If the preferred basis in quantum mechanics and/or choice of consistent histories in consistent histories is arbitrary, and can only be determined by the "questions we ask", just who exactly is this ...
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1answer
113 views

Are the limits to prediction by QM provable?

Quantum mechanics states that only two aspects of a quantum system can be predicted with certainty: 1) the average and 2) the standard deviation of many measurements of identically prepared quantum ...
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1answer
38 views

Would QM be detectable in a all boson universe

If there was a universe with the same laws as this one, but there were only bosons in it, would QM 'do anything'? Would there be any QM effects - such as an energy level (but that would require ...
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1answer
84 views

Uncertainty and wave-trains

My textbook and the following extract from feynman's lectures present the same idea regarding wavetrains and uncertainty in their wavelengths. Why is it that a wavetrain confined to some space has an ...
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2answers
156 views

If inherent randomness exist in quantum mechanics, what then of eternalism implied by relativity?

I am nothing but a curious layman so don't go too technical on me. First of all, I am well aware that a lot of people consider the question of determinism vs indeterminism to be unsolved and others ...
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1answer
84 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
168 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
369 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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2answers
123 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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0answers
77 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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0answers
39 views

Realistic interpretations of quantum entanglement: Are there alternatives to the “Transactional Interpretation”?

Quantum entanglement bridges space and time: entangled particles show correlations independently of where and when they are measured. This is most evident in "delayed choice quantum eraser" ...
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0answers
22 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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2answers
84 views

Are there any non-interpretational arguments in favour of Everetts Many-Worlds?

As far as I understand Everetts Many-Worlds he makes the case for a realist theory of QM at the enormous cost of many-worlds. Are there any arguments in favour of Everetts interpretation that makes ...
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0answers
122 views

Does the Delayed Choice Quantum Eraser experiment prove consciousness causes collapse?

https://www.youtube.com/watch?v=H6HLjpj4Nt4 This question comes from the video above. If you don't want to watch the video, I'll cut to the chase. Essentially, it claims the Delayed Choice Quantum ...
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0answers
56 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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0answers
79 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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0answers
162 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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42 views

Showing that the CHSH inequality is not violated

I can usually work out whether CHSH inequality is violated when the observables that we are measuring and the state we are in is given explicitly, but I'm struggling with the generality of the ...
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0answers
76 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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0answers
45 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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0answers
122 views

Question regarding the Bohm interpretation

I tryed to understand the Bohm interpretation and this is what picture appeared to me. Please tell me if I understood something incorrectly. All particles have definite positions and follow ...
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0answers
198 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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4answers
501 views

Do multiple electrons exist during superposition?

Wikipedia says: Quantum superposition is a fundamental principle of quantum mechanics that holds that a physical system—such as an electron—exists partly in all its particular, theoretically ...
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1answer
59 views

Many worlds interpretation

I think many worlds interpretation is inconsistent with the EPR paradox. Quantum mechanics says that particles are really in more places at the same time and the particle is really only probability ...
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2answers
383 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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1answer
63 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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1answer
355 views

Quantum superposition and fate [closed]

First of all, sorry for my knowledge of physics. Maybe my question is too obvious but I want to ask it. I am thinking about fate and if it exist or no. According to my assumption if I take any ...