0
votes
2answers
54 views

Question on the logical structure of the EPR argument and Bell's inequalities

Recently I have read a lot online about the EPR argument and Bell's inequalities and its implications. When comparing what people write there online with the actual research articles of Einstein and ...
0
votes
0answers
45 views

Quantum entanglement, principle of locality and speed of light

I know it's a newbie question but I was wondering about how the principle of locality and the speed of light's limit fit with the phenomena of quantum entanglement? I've read that, due to Bell's ...
2
votes
4answers
124 views

Principle of locality

Why does the principle of locality have so such great importance in physics that theory should be consistent with it?
7
votes
2answers
468 views

Bells 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 ...
1
vote
0answers
79 views

Does nonlocal theory violate causality?

Let's talk about two kinds of nonlocal theories. The first one frequently derives from integrating out part of the degrees of freedom to obtain a kind of effective theory. Probably, we get an integral ...
1
vote
3answers
171 views

Non-locality and quanta

Quantum mechanics is non-local in that long distance correlations are present, though there is no signalling possible. But QFT is Lorentz invariant and contains quantum mechanics as a special case. I ...
3
votes
2answers
109 views

Are locality and separability two distinct notions?

Is there any difference between locality and separability in quantum mechanics, or do they mean the same thing? It seems authors do not always agree.
0
votes
2answers
323 views

Does this Bell's experiment actually disprove Local Hidden Variable Theories (LHVT)

I'm watching some archived video lectures on QM in Coursera given by Umesh Vazirani from UC Berkeley and I have a question regarding a Bell's experiment (I guess something close to this) described in ...
0
votes
1answer
100 views

Other ways of checking whether particular system result in non-locality

In quantum mechanics, when hamiltonian $H$ is constrained ($H = \sqrt{m^2 - \hbar^2 \nabla^2} $) so that it would produce simple "relativistic" model of quantum mechanics, we can show that it results ...
1
vote
2answers
210 views

$\nabla$ and non-locality in simple relativistic model of quantum mechanics

In Wavefunction in quantum mechanics and locality, wavefunction is constrained by $H = \sqrt{m^2 - \hbar^2 \nabla^2} $, and taylor-expanding $H$ results in: $$ H = \dots = m\sqrt{1 - \hbar^2/m^2 ...
3
votes
1answer
325 views

Wavefunction in quantum mechanics and locality

Every wavefunction of a form $\Psi(x)$ can be described as a superposition of multiple free particle solutions. We can see the following Fourier transform: $$ \psi(x) = \int e^{ik\cdot x} \psi(k) dk ...
16
votes
2answers
2k views

Definitions: 'locality' vs 'causality'

I'm having trouble unambiguously interpreting many answers here due to the fact that the terms locality and causality are sometimes used interchangeably, while other times seem to mean very different ...
7
votes
1answer
358 views

How is the 'cluster decomposition principle' implemented in holographic theories?

Since holographic theories are non-local by definition, how is this principle implemented? Naively, it seems to me it is not, at least, in some sense. I would appreciate an explanation as simple ...
1
vote
2answers
258 views

What's the relationship between quantum entanglement and the relativity of time?

Apologies in advance for what may be a stupid question from a layman. In reading recently about quantum entanglement, I understood there to be a direct link between entangled particles, even at ...
1
vote
1answer
295 views

EPR paradox and uncertainty principle

In Wikipedia article EPR paradox, The original paper purports to describe what must happen to "two systems I and II, which we permit to interact ...", and, after some time, "we suppose that there ...
1
vote
0answers
120 views

Non-Locality and Entanglement

Let’s consider a pair of particles [with their signals] comprising an isolated system. Any change in some property of either particle is due to the signal/s received from the other. Each particle has ...
11
votes
3answers
802 views

Bell's theorem and why nonlocality is problematic

I generally hear it assumed that Bell's inequality implies violation of counterfactual definiteness, because locality is considered sacrosanct. I understand of course that measurable violations of ...
4
votes
3answers
630 views

Assumptions in Bell's Theorem

It is often Stated that Bell's Theorem is equivalent to the statement: No theory of Local Hidden Variables can reproduce all of the predictions of quantum mechanics. I see nowhere in Bell's Theorem ...
0
votes
1answer
314 views

Relativity and Entanglement

Say we have two particles which are entangled so that they have opposite spins. If one is up, the other is down. They are sent off to two spatially separated observers A and B. Both observers can ...
5
votes
4answers
643 views

Locality in Quantum Mechanics

We speak of locality or non-locality of an equation in QM, depending on whether it has no differential operators of order higher than two. My question is, how could one tell from looking at the ...
2
votes
4answers
237 views

Are Everettian branchings global or local?

Everett's theory of quantum mechanics is about the wavefunction of the whole universe holistically. If a branching occurs very far away at the Andromeda galaxy, do I also branch? Are branchings global ...
14
votes
5answers
1k views

What combinations of realism, non-locality, and contextuality are ruled out in quantum theory?

Bell's inequality theorem, along with experimental evidence, shows that we cannot have both realism and locality. While I don't fully understand it, Leggett's inequality takes this a step further and ...
40
votes
8answers
7k views

Why quantum entanglement is considered to be active link between particles?

From everything I've read about quantum mechanics and quantum entanglement phenomena it's unobvious for me, why quantum entanglement is considered to be active link. I.e. it's stated every time that ...