All Questions
59 questions
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Does Bell’s theorem rule out changing hidden variables?
In the EPR experiment, it is said that there are predictions that are made if there are hidden variables determined by something locally in each particle that results in a correlation in entanglement. ...
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3
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173
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Can there be a local hidden variable theory that works differently for each electron in an entangled pair?
I recently watched a video from Brian Greene that goes over an example of Bell’s inequality. Video here. In this example, he imagines the generation of a pair of entangled particles, each of which is ...
user383648
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2
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A question about Born's rule in the Many-worlds interpretation
Can somebody explain the idea of self-locating uncertainty when there's a binary choice of eigenstates for an entanglement? I understand the idea that because you are unsure of which branch you are in,...
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1
answer
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Is there any minimalistic version of superdeterminism theory?
Superdeterminism is one wild conjecture which is an alternative to the standard quantum mechanical interpretation and preserves local realism
Superdeterminism seems to be too much of a stretch. If ...
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2
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Quantum Entanglement: Is Non-locality Inherent or Does It Violate Causality? [duplicate]
Dear Physics Stack Exchange community,
I am intrigued by the concept of quantum entanglement and its implications for our understanding of the fundamental nature of reality. I have come across various ...
-2
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2
answers
227
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What's mechanism of "spooky action at the distance"? [duplicate]
Nobel prize 2022, a local theories of hidden variables are ruled out, Einstein's "spooky action at a distance" seems to be a reality.
Is there ANY explanations of this behavior of quantum ...
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4
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138
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Is the interference pattern of an entangled particle affected by the measurement of it's pair far enough away to take into account special relativity?
I've been considering a theoretical setup for a quantum experiment where 2 particles are prepared with entangled spin. They are then moved far away from one another where particle B is next to Bob who ...
8
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2
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In quantum mechanics, can we measure anything else than position?
In the basic quantum mechanics lectures, we learn that we can measure any observable. That means mathematically, all Hermitian operators correspond to a physically measurable quantity. In strong ...
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1
answer
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Is my interpretation of the underlying idea behind this 2022 Nobel Prize story “How physicists proved the universe isn’t real” more or less accurate?
I’m not very good at math but I frequently watch PBS Spacetime on YouTube to try to satisfy my curiosity about physics despite that.
In a recent video by Dr Ben Miles titled “How Physicists Proved the ...
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3
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412
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Don't Bell experiments rule out local non-realism too? [duplicate]
Bell experiments rule out local realism (hidden variables). But it seems to me that it also rules out local non-realism (no hidden variables).
Local non-realism makes 2 claims;
Two distant events can'...
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votes
1
answer
125
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The intepretation and maths behind the many-worlds interpretation of quantum mechanics
recently I started reading the book "Something deeply hidden" by Sean Caroll. In the book he talks about the many-worlds interpretation of quantum mechanics as a more elegant way of thinking ...
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1
answer
481
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How does the many-worlds interpretation solve spooky action at a distance?
If we take the classic example of two particles that are entangled with up spin and down spin, and we separate these particles a few light years apart and then observe them one after the other, they ...
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1
answer
658
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Karen Barad's theory of agential realism - does it stand on solid scientific ground or is it quantum quackery? [closed]
Before you vote to close this question as off-topic, please note that while my interest in the topic lies on the metaphysical guesswork, my question here is specifically about Karen Barad's scientific ...
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6
answers
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Quantum Physics: Are entangled electrons in absolute states?
I was having a discussion about quantum physics with a friend, and we came to realise that we perceived the same situation in two very different ways. After searching online, we still weren't able to ...
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4
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3
answers
458
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Many Worlds locality and EPR experiment
I've read in Sean Carroll's book (Something Deeply Hidden) that the Many-Worlds interpretation of quantum mechanics might be the only way to avoid instantaneous effects of entanglement, by having the ...
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2
answers
316
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How does the many-worlds interpretation look like in bra ket notation?
If I understand correctly the many worlds interpretation says the universe is continously splitting into multiple branches and quantum measurements occur when decoherence causes a quantum state to ...
1
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0
answers
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Are there known paradoxes regarding a detector that was, before use, entangled with a particle it detects?
Is it possible to design a system where a detector is entangled with the particle state it detects (before it is detected), and to create a paradox from this?
Upon observance of a state by the ...
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0
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107
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How to imagine wavefunction branching?
This is a question particularly geared toward the Many Worlds interpretation, but I think it could be translated to other approaches as well.
I am not sure I understand exactly what sort of events ...
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2
answers
1k
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How is the non-local nature of quantum entanglement explained?
From what I understand, Einstein tried to introduce real but hidden variables to remove the apparent non-local nature of quantum entanglement, but Bell's inequality showed local realism isn't possible....
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2
answers
236
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Quantum Bayesianism and the Copenhagen interpretation
Is Quantum Bayesianism (QBism) preferable than the Copenhagen interpretation of QM?
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0
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93
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Why would the classical (local) correlation in Bell's experiment rule out the cosine of the angle?
This question expands on a specific detail of this previous question:
Why would classical correlation in Bell's experiment be a linear function of angle?
I would have commented on/answered that ...
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vote
1
answer
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Is it possible to classify "branches" in the MWI of QM? [closed]
In Everett's Many Worlds Interpretation of QM, what would be classified as a "world" or a "branch"?
Would the "reality" of what I'm consciously experiencing be distinguishable from a separate "...
2
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3
answers
238
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How does disregarding realism but maintaining locality explain the Bell Experiment?
If we conduct a simple Bell experiment, we can show that "hidden attributes" are inconsistent with the probabilisitic distribution of results that we get in an Alice/Bob type game played with ...
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0
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What are the best resources to master Quantum Entanglement?
I am reading Modern Quantum Mechanics by Sakurai for my semester. I read about the Quantum Entanglement, Bell Inequality and Hidden Variables theory, EPR Paradox etc. and got fascinated. I just wanna ...
1
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2
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147
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Are wave functions built of other wave functions?
I have heard the term wave function used in a number of contexts describing both quantum objects (electrons, etc) and more macroscopic objects (atoms, birds, cats, etc). Is it correct to say a lithium ...
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vote
1
answer
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Why do we see particles in the many-worlds interpretation?
I am starting to feel like I have a decent grasp on the MWI, but a piece of it keeps bugging me. My understanding is that quantum objects are kind of spread out and wavy until something comes along ...
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2
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171
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Why does the effect of measuring an entangled particle is not apparent when examining only one particle? [closed]
As far as I understand, the Bell test experiments show that observations (measurements) of entangled particles have an effect on one another.
This effect is apparent when examining the results of ...
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0
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Scan Quantum mechanics: Status of current research
I recently stumbled on a new interpretation of Quantum mechanics, called Scan Quantum Mechanics, given by Beatriz Gato-Rivera. She suggests a quantity called quantum inertia, which divides the ...
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2
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160
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Does something prevent superposition at our scale?
I often encounter the argument that quantum mechanics reduces to classical mechanics at sufficiently big scales, as soon as h becomes sufficiently small respect to the actions involved. I clearly ...
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1
answer
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What is the reason for the reported opposite-of-QM handedness of photons in a Bell test with circularly polarized photons? [closed]
In https://file.scirp.org/pdf/OPJ_2016111414355792.pdf, a Bell test using circularly-polarized photons is reported. The data shows that coincidences happen in the reverse handedness predicted by ...
- 1,175
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2
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170
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Are all Bell tests valid only for linearly-polarized photons? [duplicate]
In https://arxiv.org/abs/1407.2605, it is argued that all photons are necessarily circularly polarized, and linearly-polarized photons must be a superposition of such circularly-polarized photons. ...
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23
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6
answers
6k
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How do we know that entanglement allows measurement to instantly change the other particle's state? [duplicate]
I have never found experimental evidence that measuring one entangled particle causes the state of the other entangled particle to change, rather than just being revealed.
Using the spin up spin down ...
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1
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356
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How does the Many-Worlds Interpretation of Quantum Physics relate to Consciousness? [closed]
According to the Many-Worlds Interpretation of Quantum Mechanics, each quantum event causes the world to "branch" into a superposition of outcomes.
How come "my" consciousness only chooses one of ...
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0
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61
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Justification for "which path" inference in Hardy's paradox?
I'm going over Hardy's paradox again recently and whenever I try to think about it I always get confused with the classical part of the analysis. Just as a brief summary, the setup of the paradox is ...
- 503
11
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3
answers
8k
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What are non-local hidden variables?
It is said that Bell's Inequality basically denies all possible local hidden variables theories as solutions to entanglement but what does a non-local hidden variable theory mean and how does it get ...
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3
answers
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When light reflects off a mirror, does the wave function collapse?
This question is specific to the Copenhagen interpretation, which states that the wave function collapses on interaction. If we have a beam of light reflected off a mirror, whether you see this light ...
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1
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Will a particle still be in a superposition state if unobserved from only the perspective of one observer?
In this scenario let us take a particle that can have either spin up or spin down. Let's say that observer 1 observed the particle's spin to be down. But observer 2 hasn't observed it yet. So, then ...
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0
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249
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Are all instances of quantum non-locality problem artifacts of the use of classical concepts in quantum physics?
Consider experiments involving entangled spins, say two-spin 1/2 particles in the singlet state:
$$\left|\psi\right> =\frac{1}{\sqrt{2}}\left[\left|\uparrow\downarrow\right> - \left|\downarrow\...
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votes
2
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242
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Spooky-action-at-distance, why it was claimed by Einstein?
If I understand "popular quantum mechanics" right, there is no faster-than-light communication via two entangled particles, because changing one of the particles (with the purpose to transfer a signal ...
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1
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Why does entanglement not imply hidden variables?
By the causal symmetry of spacelike-seperated events, the statement "measurement of particle 1 causes subsequent collapse for particle 2" is equivalent to "measurement of particle 2 causes subsequent ...
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1
answer
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Bell's theorem and how it solves the EPR paradox
Could someone explain to me how Bell's theorem solves the EPR paradox and 'spooky action at a distance'?
From what I understand, when measuring a state, say spin up in the x direction, the wave ...
1
vote
1
answer
348
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Is there a difference between observation and entanglement?
I have very basic knowledge about quantum mechanic. I started wondering if there is any difference theoretically between observation and entanglement between subject and object.
I.e. if we simplify ...
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1
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Since photons do not experience time (nor distance in that case), why did Einstein think it was "spooky action at a distance"? [closed]
A photon travels at c, so it experiences no time or distance. I imagine from the photon's perspective, it's rather just like a simple dot on some kind of 4D manifold. So it begs the question of why ...
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262
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Why is the wavefunction not a hidden variable?
Consider the following standard case of an entanglement experiment:
We prepared two electrons A and B with states
$$\lvert A\rangle=a_1\lvert \uparrow\rangle+a_2\lvert \downarrow\rangle$$
$$\lvert B\...
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1
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64
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What happens that doesn't allow our measurement?
Suppose pair production results in an electron and positron pair in an entangled system.
One person (A) measures the electron and another person (B) measures the positron. Another property of this ...
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1
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Pilot waves and quantum eraser; pilot wave simulation
I recently watched this video about the quantum eraser experiment on PBS spacetime: Link. Has an experiment like the quantum eraser been tried with the pilot wave theory, ie bouncing droplet ...
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votes
2
answers
828
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When does the world split in MWI
I've been reading Eliezer Yudkowsky's blog post regarding decoherence and many worlds, and although he is not a physics but a strong proponent of MWI, I can basically see why he feels that MWI is a "...
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2
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343
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What stands behind the quantum nonlocality appearing in entanglements, and why Bell's inequalities are violated?
I noticed the question whether Bell's inequalities are based on a false premise,
(https://physics.stackexchange.com/questions/219904/could-bells-theorem-be-based-on-a-false-premise) but I bring ...
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2
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115
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In quantum mechanics does the truth/accuracy of a measurement really matter?
Once John Wheeler said "the past has no meaning or existence unless it exist as a record in the present". So, in a experiment of delayed choice entanglement swapping, if we used a faulty detector to ...
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306
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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 ...
