All Questions
61 questions
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Can somebody explain to me one of the Bell experiments?
I can't understand the experiment in this paper.
In this experiment, two electrons at different points $A$ and $B$ are entangled with one photon each. Then, the photons are entangled in point $C$ ...
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6
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What was the fallacy in EPRs chain of arguments?
Let's say, there is an entangled system of two electrons with opposite spins; The joint system is in a state of eigenvectors for z-Spin ( $S_z$) with both particles far away from each other:
$$|\Psi\...
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1
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Mermin's EPR paradox explanation [closed]
I am reading N. D. Mermin, Bringing home the atomic world: Quantum mysteries for anybody
. The main part of the article is pretty clear to me. But I am not sure how quantum mechanics described in ...
- 1,060
2
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1
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299
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Measurement of the spin of the EPR pair in two orthogonal directions and how did Einstein tackle this?
Let us consider two types of measurement in the EPR experiment. In Bohm's description of this experiment, the state of the electron-positron (called the EPR pair) is given by
$$
|{\rm EPR} \rangle =\...
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2
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Is the possible Bell's test loophole of entangled particles communicating at a non instantaneous but FTL speed addressed and eliminated? [closed]
TLDR:
There seems to be a loophole in Bell's test that is not addressed or eliminated before we can successfully conclude that it proves that the Universe is unreal and non local. The entangled ...
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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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1
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247
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How can we be sure Bell's theorem disproves local realism when we are not sure whether the measuring apparatus is in some form of entanglement or not? [duplicate]
Bell's therorem seems to disprove localism because measuring, let's say spin of an entangled electron, seem to communicate the measurement to it's another pair instantaneously.
But isn't another thing ...
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2
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What is the difference between the EPR paradox and Bell's inequalities?
I am a newbie here, hope I will be able to get accustomed on this forum.
I am trying to understand what quantum entanglement is. Obviously, for this it is very useful to understand Bell's theorem. ...
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1
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159
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Operation on one of the EPR particles [closed]
Sabine Hossenfelder, a science YouTuber, talks about asking the following question to ChatGPT in one of her videos:
If you perform an operation which is not a measurement on one particle in a pair of ...
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40
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In observing EPR phenomenon, which direction is opposite to the other?
I have a question about the EPR phenomenon of the quantum-mechanics.
When you observe the EPR phenomenon, you separate two spins in the singlet state. Then, you and your fellow independently observe ...
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2
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86
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The eigenstates of a single EPR particle
I am curious whether there is a sense in which each of the EPR particles is in an eigenstate of some observable.
Consider a pair of EPR particles 1 and 2, of which combined state is given by
$|\Psi\...
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30
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6
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33k
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Bell's theorem for dummies, how does it work?
I've been reading up on theoretical physics for a few years now and I feel like I am starting to get an understanding of particle physics, at least as much as you can from Wikipedia pages. One thing ...
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3
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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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87
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Is the ER=EPR conjecture a loophole in Bell's theorem that would allow for local realism to hold?
Specifically, if it turned out the mechanism for quantum entanglement is that all particles are somehow connected to each other via wormholes (assuming that is what the conjecture actually says), it ...
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1
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159
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A question regarding quantum entanglement
According to wiki,
Quantum entanglement is the physical phenomenon that occurs when a group of particles are generated, interact, or share spatial proximity in a way such that the quantum state of ...
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2
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112
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Quantum Entaglement and EPR [closed]
I was studying the EPR Paradox and Bell's theorem . My question is how does this information travel between two entangled particles, has there been any research into this?
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3
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421
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What is meant by the term "elements of physical reality" used by EPR paper?
I was thinking about the phenomenon of quantum entanglement. The widely accepted view of nature of reality is that of copenhagen interpretation(please correct me if I am wrong!) while Einstein pointed ...
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The choice of measurement basis on one half of an entangled state affects the other half. Can this be used to communicate faster than light?
It is often stated, particularly in popular physics articles and videos about quantum entanglement, that if one measures a particle A that is entangled with some other particle B, then this ...
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1
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1
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240
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QBism and causes of EPR correlation
I wish to clarify my understanding of the QBist (eg Fuchs et al), or Quantum Bayesianism, interpretation of quantum mechanics and in particular its approach to the EPR problem.
Suppose we consider a ...
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2
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398
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Reality, locality, and universality in the EPR paradox
Apologies if this has been asked before. I did some searching but didn't see it anywhere asked quite like this. Thanks in advance for any insights.
Caveat: I am an organic chemist and thus ...
user223099
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6
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3k
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What was the need for doing experiments to prove quantum entanglement?
This question comes from someone who is interested in Physics but with no theoretical background.
In 1936, EPR presented the thought experiment which later came to be known and quantum entanglement.
...
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2
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2
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386
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What is the local, non-realist explanation of EPR correlations?
Bell's theorem proves that local hidden variables theories cannot reproduce quantum mechanics (with the exception of superdeterministic theories). Are there any local theories that do not involve ...
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4
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771
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What is wrong with violation of locality (EPR paradox)?
When studying the EPR paradox, at some point we must resign ourselves that Reality and Locality can not be both true in the current theory of quantum mechanics.
A lot has been said in Physics.SE about ...
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Specifications of Bell's inequality experiments conducted untill now
Has any Bell's inequality experiment, conducted until now, which has satisfied the following criteria?
Having more than three measuring orientations. In the typical experimental setup I have seen ...
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2
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210
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What's the physical meaning of a reduced density matrix in EPR?
Consider an EPR situation in which there are two particles, a and b, of which state is given by
$\Psi = \frac{1}{\sqrt2}(|1\rangle|0\rangle + |0\rangle|1\rangle)$,
where $|0\rangle$ and $|1\rangle$ ...
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2
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Entanglement and Mixed States
The Wikipedia page for "Density Matrix" (https://en.wikipedia.org/wiki/Density_matrix) takes each of a pair of entangled photons as an example of a mixed state:
A radioactive decay can emit ...
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1
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166
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Question on the creation of an entangled photon pair in a specific realization of the EPR-Bohm Experiment
In a student experiment the following assembly is used to create an entangled photon pair.
From the left, a laser beam polarized along $\frac{\hat{x}+\hat{y}}{\sqrt{2}}$ is incident on a pair of BBO ...
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0
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177
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Experimental Implications of Wigner Distribution
I'm interested in the experimental implications of the Wigner quasiprobability distribution in quantum physics, but haven't been able to find anything that addresses my particular question.
...
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6
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1k
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What counts as information?
What counts as information? In e.g. the EPR experiment why is one entangled particle knowing instantaneously the state of the other not counted as 'information'.
Edit
Following a discussion in the ...
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10
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Is quantum entanglement mediated by an interaction?
You can get two photons entangled, and send them off in different directions; this is what happens in EPR experiments. Is the entanglement then somehow affected if one puts a thick slab of EM ...
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1
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Measurements of spin correlations: Alice goes back to Bob and compares results
Take a fully entangled two-photon state, like
$|\Psi>=\frac{1}{\sqrt{2}}\big(|+->-|-+>\big)=\frac{i}{\sqrt{2}}\big( |yx> - |xy> \big)$
where one photon is sent to Bob and the other to ...
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1
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107
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EPR related question
Suppose two entangled electrons are emitted from a source. After traveling a long distance in opposite directions, each electron passes through separate but otherwise identical double slits. Will both ...
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2
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594
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What makes particles lose entanglement or do they ever lose it?
Once we generate a pair of entangled electrons or photons, will they ever lose their entanglement?
If yes, then what causes them to lose entanglement?
If measuring them causes them to lose ...
user218113
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0
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67
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What's the definition of the EPR limit?
I am reading this paper, nature.com/articles/s41567-018-0347-x, which is about the generation of high-dimensional entanglement using two non-commuting variables, frequency-bin and time-bin.
On page 7 ...
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3
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224
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Does the EPR paradox assume that entangled particles leave each other's light cones, or not?
So I was reading this post by Ethan Siegel, which introduces a recent talk by Lee Smolin. In the article, Siegel outlines the EPR paradox (or something like it) and mentions that it is based on the ...
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EPR Paradox clarification
Basically, the paradox works like this:
Two entangled particles (A and B) are a light year apart.
1. Measure the X spin of A
2. Measure the Z spin of B
You ...
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0
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59
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Expected value in EPR
I was trying to read this paper http://philsci-archive.pitt.edu/3714/1/epr-bell-iep-preprint.pdf and I would like to prove the Equations (1), (2) but I am not so good for quantum mechanics so I would ...
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6
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420
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EPR paradox: instantaneous vs very fast?
An EPR quantum experiment can be explained by instantaneous collapse of the wave function regardless of the distance separating a pair of entangled particles. But do we have the certainty that the ...
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2
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95
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How does EPR pair shows simultaneously two defined values?
In the paper "Can Quantum-Mechanical Description of Physical Reality Be Considered Complete ?", it implies that with an entangled state it is possible to know two physical quantities simultaneously. ...
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1
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183
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The non-locality of Quantum Mechanics
I often heard physicists mentioning the EPR paradox or the quantum entanglement when talking about the non-locality of quantum mechanics, but wasn't quantum mechanics already non-local from the ...
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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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0
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113
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In quantum teleportation when exactly the original EPR pair stops being entangled?
In quantum teleportation Alice and Bob share a pair of entangled particles (EPR pair made of particles 2 and 3, for example). Alice has another particle (1) whose quantum state she wants to send to ...
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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 ...
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2
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226
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Is the spin in quantum entanglement set at the moment the particles are separated, instead of when measured? [closed]
Is the spin in quantum entanglement set the moment the particles are separated, instead of transmitted instantaneously to its twin particle at the time of measurement? Wouldn't this make more sense ...
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6
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915
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Explanation for the EPR-like paradox
I am trying to understand the process of Quantum Entanglement for use in Quantum computers.
The problem I have is this:
Suppose some nuclear process emits an electron-positron pair. Now after ...
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3
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640
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Quantum entanglement, how do we know there was no spin? [duplicate]
Im not a scientist, so go easy on the explanation!
As I understand it we can create two entangled particles. The entangled particles have a spin property which is opposing. When we measure one of the ...
0
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0
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301
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How are joint measurements of quantum states realized experimentally?
I have a question regarding the experimental implementation of joint measurements of quantum states.
While I understand for example the teleportation protocol using Bell states, something that still ...
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2
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47
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What's the meaning of distant measuring?
this is the context:
Einstein, Podolsky, and Rosen concluded that there are two possibilities in the case of the spinning particles. Either (a) there is some mysterious, nonlocal interaction that ...
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6
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683
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Local EPR-experiments with photons in vacuum?
The principle of non-locality states "that an object is influenced directly only by its immediate surroundings." (Wikipedia)
When two entangled particles are measured in an EPR experiment, we ...
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4
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783
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Why isn't quantum entanglement just a lack of information?
From this question and answer from joshphysics, I didn't understand one thing, even after reading the comments:
Why should assume that entangled electrons will only "decide" their state after ...
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