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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7
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3answers
390 views

How would a realist interpretation of the Mermin-Peres square look like?

How would a realist interpretation of the Mermin-Peres square with counterfactual definiteness and the existence of states prior to measurements look like?
1
vote
1answer
201 views

Question regarding the Bohm interpretation [closed]

I tried 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 ...
10
votes
3answers
2k views

Is the collapse of the wave function inherently time asymmetric?

Schroedinger's equation, as we all know, is time symmetric. In quantum field theory, we have to come up with a more sophisticated CPT reversal, but the essential point remains unchanged. However, the ...
2
votes
2answers
150 views

What does density operator being same for two sytems tells us?

Yesterday I asked a question. I got it that if a density operator is given as $$\rho=\sum_{i=1}^{i=k}p_i|\psi_i\rangle \langle\psi_i| \tag{1}$$ then it means that the system is one of the states ...
1
vote
0answers
55 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 ...
1
vote
1answer
132 views

Interpretations of Stern-Gerlach experiment

In many textbooks (J.J. Sakurai for instance) S-G experiment is explained through the idea of a collapse of a state of a system. So here, in this discrete case, we can see quantum behavior more ...
4
votes
2answers
180 views

Without apparatus can we say that the system is measured(decohered) by the environment?

"Einselection" and "tridecompositional uniqueness theorem" seem to resolve the preferred basis problem. But the premise is that there are three parts in discussion.(system, apparatus, environment) ...
23
votes
6answers
1k views

Simple example showing why measurement & interaction are different

Does someone know of a clear (pedagogical) example where one can really see(with the math) where interaction and measurement are not synonymous in quantum mechanics? I know that every measurement ...
21
votes
4answers
545 views

Is every quantum measurement reducible to measurements of position and time?

I am currently studying Path Integrals and was unable to resolve the following problem. In the famous book Quantum Mechanics and Path Integrals, written by Feynman and Hibbs, it says (at the beginning ...
9
votes
7answers
787 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 ...
5
votes
0answers
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.
-1
votes
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?
2
votes
1answer
110 views

Do electrons have a location before they are observed/measured? [closed]

Is this in all interpretations of QM? What about interpretations that are realist (MWI, penrose, ect)?
0
votes
1answer
136 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 ...
2
votes
5answers
634 views

On the foundations of quantum physics

Quantum physics has to be validated by experiments. But experiments are to be interpreted in the context of quantum physics. Isn'it like a snake biting its own tail? For example, using a scanning ...
1
vote
1answer
65 views

Does the difference between contextuality, nonlocality and retrocausality depend on where we draw the boundaries? [closed]

Suppose we have a quantum system and a measuring apparatus in a superposition of detector settings. Different detector settings would measure "complementary" properties of the quantum system. The act ...
0
votes
0answers
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 ...
3
votes
1answer
82 views

Are there any viable toy models of superdeterministic quantum mechanics?

As far as I know, superdeterminism in quantum mechanics is only considered as a theoretical possibility. Are there any fleshed out superdeterministic toy models so far which isn't nonlocal?
2
votes
3answers
130 views

What is the splitting structure of a state in thermal equilibrium in MWI?

What is the splitting structure of a state in thermal equilibrium in the many worlds interpretation? This is a mixed state, but we can perform a purification of it by doubling the system and forming a ...
1
vote
0answers
58 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 ...
2
votes
0answers
212 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 ...
7
votes
1answer
171 views

Has the Copenhagen Interpretation remained accurate?

Almost a century past, has the Copenhagen Interpretation (CI) undergone any modification? In other words, has any of its underlying principles been reformulated since? The notable (usual) examples ...
4
votes
2answers
159 views

Is there an idealist rather than realist interpretation of QM?

The many-worlds interpretation of QM is a realist explanation as it makes the wave function of the universe real. That is it makes the probabilities of outcomes real outcomes. One could argue that ...
13
votes
5answers
2k views

Consequences of the new theorem in QM?

It seems there is a new theorem that changes the rules of the game in the interpretational debate on QM: http://www.nature.com/news/quantum-theorem-shakes-foundations-1.9392 Does this only leave ...
4
votes
3answers
2k views

Why is Wheelers Delayed Choice Experiment Incorrect?

I have come across 'Wheelers Delayed Choice Experiment' which tries to prove that you can work out which Slit a Photon Goes Through in the Double Slit Experiment. But I thought it was impossible to ...
1
vote
2answers
96 views

Does information paradox in the Many Worlds interpretation cause a problem? [closed]

I'm taking a philosophy of time travel class. In one of the lectures, the teacher was discussing problems with the Many Worlds interpretation. He talked about how since anything that can possibly ...
0
votes
3answers
284 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 ...
1
vote
1answer
230 views

Do consciousnesses get “scattered” across the many worlds of the MWI?

According the many worlds-interpretation (MWI) of quantum mechanics, following a decision with possible outcomes $A$ and $B$, with respective probabilities $p_A=P(A)$ and $p_B=P(B)$, a proportion ...
10
votes
2answers
204 views

Quasiparticles in Bohmian mechanics

My questions are about de Broglie-Bohm "pilot wave" interpretation of quantum mechanics (a.k.a. Bohmian mechanics). Do quasiparticles have any meaning in Bohmian mechanics, or not? Specifically, is ...
2
votes
1answer
226 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 ...
1
vote
6answers
231 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, ...
11
votes
4answers
617 views

What is an interpretation of quantum mechanics?

In the sense of "Copenhagen Interpretation", what exactly is an interpretation? What purpose does an interpretation serve? Can an interpretation be tested or even be correct or incorrect independent ...
2
votes
1answer
228 views

Why no Top Physicists Work on Bohmian Mechanics? [duplicate]

I'm curious to hear some opinions from serious physicists on this site as to why no top physicists have ever worked on Bohmian Mechanics. Except Bohm and Bell, the theory has received virtually no ...
1
vote
1answer
138 views

Argument for proving that the universe must be indeterministic [duplicate]

Can there exist an argument that could be used for proving that the universe is indeterministic? If this one seems to be too strict (rigorous), I would also be interested to know a 1-sentence ...
2
votes
2answers
4k views

What is wrong with the De Broglie–Bohm theory a.k.a “Causal Interpretation” of quantum theory? [duplicate]

Possible Duplicate: Why do people still talk about bohmian mechanics/hidden variables I've heard of De Broglie–Bohm theory a.k.a causal interpretation of quantum theory. The predictions ...
2
votes
1answer
211 views

What obstacles does de Broglie's pilot theory have to overcome? [duplicate]

I have been reading through a Wired article on pilot wave theory which talks about new evidence in support of Louis de Broglie's concept of pilot theory through experiments showing that the droplet in ...
1
vote
3answers
201 views

Why does the Copenhagen interpretation assert randomness if this cannot be tested?

Why does the Copenhagen interpretation of QM assert that random events occur if such a claim cannot ever be proven or disproven? A related question: How to tell if QM is really random? Edit On ...
6
votes
1answer
1k views

What is the meaning of the Fourier transform of Feynman propagator?

I know $K(a,b,t)$ is the probability amplitude that a particle that starts at point $a$ is found at point $b$ at a time $t$ later. There is also an expression that sometimes is called green function: ...
1
vote
0answers
82 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: ...
0
votes
0answers
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 ...
0
votes
0answers
96 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 ...
2
votes
3answers
401 views

A question on quantum computing and de Broglie's pilot wave theory

I don't know much about quantum computing except what I have read about on wiki and popsci. I have been reading about the de Broglie-Bohm pilot wave theory and how they describe quantum mechanics in ...
2
votes
3answers
270 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 ...
2
votes
3answers
230 views

What is the best article presenting counterarguments to a many-world interpretation? [duplicate]

I'd like to see a clear overview of why the many-world interpretation (WWI) of quantum is wrong, written by someone who believes that. This would be aimed at a technically aware audience, yet as an ...
4
votes
1answer
526 views

If there is no collapse of the wave-function does this mean that the many worlds interpretation of QM must be wrong?

If as some people suggest, there is no collapse of the wave function (is there a standard name for this position), then must one rule out the many-worlds interpretation of QM?
10
votes
9answers
1k views

What criteria distinguishes causality from retrocausality?

The brilliant philosopher David Hume remarked that if two events are always found to be correlated to each other with one event happening prior to the other, we call the earlier event the cause and ...
3
votes
2answers
193 views

Copenhagen interpretation

Reading some science history, Werner Heisenberg and Bohr created the Copenhagen interpretation, but what I didn't get is how can we connect this interpretation to Schroedinger's cat and the double ...
4
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4answers
579 views

Quantum mechanics threshold

First of all I beg your forgiveness as I am not a physicist and the question I am going to ask may sound silly. I am aware that beyond a certain threshold in the hierarchy of building blocks of ...
9
votes
4answers
2k views

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 ...
9
votes
3answers
292 views

Does quantum collapse involve a loss of information? Does it require energy as suggested by the Landauer Limit?

I read in the context of quantum computing or of the minimal energy required for computation that there has to be a minimum possible amount of energy required to change one bit of information, called ...