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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3answers
419 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 ...
2
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2answers
290 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 ...
1
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0answers
36 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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2answers
86 views

Does the many worlds interpretation eliminate the spooky action at a distance paradox? [closed]

I'm sorry if this is a stupid question. I'm a novice at physics. I have read the article about entanglement and EPR paradox. The spin of two particles is measured when they are very far apart, and ...
0
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1answer
38 views

Particle position and speed [duplicate]

If I understand correctly, particle is something at a point of time, where you can tell it's position, but what if particle is moving, then you can tell it's speed. From what I understand wave is NOT ...
0
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2answers
60 views

Spectral lines on a detector

How can it be possible for a single electron to go through 2 slits at the same time and create 2 spectral lines on a detector. What is wrong with that theory, but at the same time produce results as ...
3
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1answer
192 views

Has this experiment really demonstrated wave-function collapse?

My question is: why did the following experiment claim that it had demonstrated the wave-function collapse? http://www.nature.com/ncomms/2015/150324/ncomms7665/full/ncomms7665.html I would have no ...
8
votes
5answers
643 views

Are coherent states of light 'classical' or 'quantum'?

Coherent states of light, defined as $$|\alpha\rangle=e^{-\frac{|\alpha|^2}{2}}\sum_{n=0}^\infty \frac{\alpha^n}{\sqrt{n!}}|n\rangle $$ for a given complex number $\alpha$ and where $|n\rangle$ is a ...
1
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1answer
77 views

Flaws of Broglie–Bohm pilot wave theory?

I recently learned about an oil drop experiment that showed how a classical object can produce quantum like behavior because its assisted by a pilot wave. How has this not gained more attention? What ...
0
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1answer
105 views

Does quantum theory obey locality?

Bell's inequality together with the Aspect experiment shows that that we cannot have local realism. But does quantum theory obey locality? and if not how can locality be violated but not special ...
2
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2answers
158 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 ...
3
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1answer
208 views

How does many-worlds interpretation make measurement unitary?

Does many-worlds interpretation of QM make the process of measurement (wavefunction collapse) be an unitary transform? If so, how does it do this? If we have an "object" qubit in state ...
7
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5answers
516 views

Quantum entanglement and spooky action at a distance

When quantum entanglement is explained in "layman's terms", it seems (to me) that the first premise, that we have to accept on faith, is that a particle doesn't have a certain property (the particle ...
3
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4answers
174 views

What really is a particle?

In Classical Mechanics we consider particles as things whose internal structure for the purpose of studying some phenomenon might be neglected. In that setting we associate particles to points and ...
4
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4answers
168 views

Does quantum mechanics imply that particles have no trajectories?

In Classical Mechanics we describe the evolution of a particle giving its trajectory. This is quite natural because it seems a particle must be somewhere and must have some state of motion. In Quantum ...
-1
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2answers
98 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 ...
1
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2answers
66 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 ...
50
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5answers
23k views

Is the universe fundamentally deterministic?

I'm not sure if this is the right place to ask this question. I realise that this maybe a borderline philosophical question at this point in time, therefore feel free to close this question if you ...
9
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2answers
530 views

Should it be obvious that independent quantum states are composed by taking the tensor product?

My text introduces multi-quibt quantum states with the example of a state that can be "factored" into two (non-entangled) substates. It then goes on to suggest that it should be obvious1 that the ...
0
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0answers
47 views

Arrow of Time in Information transfer

I am writing a sci-fi script and need some legitimate theory to back up a central story element (so there's no real world application): Could there be a logically consistent theory supporting the ...
1
vote
0answers
58 views

Are there any event-based interpretations of quantum physics? [closed]

Are there any interpretations of quantum physics where we have a combination of probabilities and objective realizations of these probabilities on a very low level. The first part of my question is ...
0
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0answers
53 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 ...
1
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3answers
290 views

How does De Broglie–Bohm theory or pilot wave theory explain the results of the Stern–Gerlach experiment?

The Copehagen interpretation of QM explains the Stern–Gerlach experiment by asserting that a particle is in a superposition of states and doesn't have a definite spin until measured. However, the de ...
0
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0answers
26 views

Entanglement and the boundaries of fiction

If entanglement is just a correlation from when the particles were in proximity, and there is no causality between the two, can the state of one particle be changed after being measured, and that ...
0
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1answer
44 views

If the only observer dies, could observer 2 ever have see a different result?

My layman's understanding of QFT is that once a system is observed, any future observation will always yield the same result. Would this hold true if the original-and-only observer, without any ...
3
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3answers
99 views

Physical meaning of quantum interpretations [closed]

Do interpretations of quantum mechanics have physical meaning? An argument for no would be the fact that no matter the interpretation, one gets the same measurements. They also do not follow logical ...
3
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6answers
382 views

How do we know that there isn't a classical solution to the measurement problem/Quantum Mechanical uncertainty?

It was mentioned to me that it can be shown that there is no classical explanation for the uncertainty in Quantum Mechanics -- i.e. that there are no hidden workings that we have just not yet seen, ...
0
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2answers
196 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 ...
0
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0answers
61 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 ...
6
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5answers
750 views

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 ...
2
votes
1answer
132 views

Are only 2 bits of information transmitted in quantum teleportation?

Prompted by the recent success in Delft, I've been reading a number of papers and articles about quantum teleportation. I'm comfortable with my understanding of most aspects but haven't found much ...
0
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1answer
42 views

Relational Interpretation of Quantum Mechanics and Universal Wave Function

Why is there no universal wave function for a relational interpretation of quantum mechanics? "Quantum mechanics is a theory about the physical description of physical systems relative to other ...
2
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2answers
161 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 ...
0
votes
1answer
52 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 ...
9
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5answers
460 views

Are different interpretations of quantum mechanics empirically distinguishable?

Are the different interpretations of Quantum mechanics just different viewpoints of the same physical reality? Or can experiments distinguish them? Are they empirically distinguishable or not? I have ...
0
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1answer
142 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 ...
2
votes
4answers
1k views

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 ...
14
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9answers
2k views

“Reality” of EM waves vs. wavefunction of individual photons - why not treat the wave function as equally “Real”?

In thinking how to ask this question (somewhat) succinctly, I keep coming back to a Microwave Oven. A Microwave Oven has a grid of holes over the window specifically designed to be smaller in ...
0
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2answers
101 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 ...
0
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1answer
96 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 ...
-2
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1answer
65 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 ...
4
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2answers
136 views

Does Bell's theorem rule out the possiblity that measurements are completely determined by events in the past light cone?

I'm studying Bell's theorem and the CHSH inequality for some time. Now it's clear to me that one cannot reproduce the correlations predicted by quantum mechanics by assuming that particles carry ...
5
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5answers
730 views

Is the wave function objective or subjective?

Here is a question I am curious about. Is the wave function objective or subjective, or is such a question meaningless? Conventionally, subjectivity is as follows: if a quantity is subjective then ...
0
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2answers
60 views

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 ...
2
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0answers
179 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 ...
0
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6answers
544 views

Could this mean that Schrodinger's Cat thought experiment is false?

Since it is uncertain on whether or not the cat could be dead or alive, it is concluded that it depends on the observer to make it either dead or alive. But lets look at a clock. It doesn't take ...
5
votes
2answers
768 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 ...
1
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0answers
36 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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0answers
19 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 ...
4
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1answer
196 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 ...