Questions tagged [epr-experiment]

A thought experiment initially proposed to argue that the description of physical reality provided by quantum mechanics was incomplete. It involves a pair of particles prepared in an entangled state; if the position of the first particle were measured, the result of measuring the position of the second particle could be immediately predicted.

Filter by
Sorted by
Tagged with
1 vote
1 answer
52 views

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 ...
user avatar
  • 11
0 votes
0 answers
34 views

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 ...
user avatar
  • 1
1 vote
1 answer
75 views

Clarification on the Premises of the Einstein-Podolsky-Rosen Argument

In their famous EPR paper, Einstein, Podolsky and Rosen argue that quantum mechanics does not provide a complete description of physical reality. To do this, they make two key assumptions: in a ...
user avatar
  • 13
1 vote
2 answers
79 views

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 $|1\rangle$ ...
user avatar
0 votes
1 answer
33 views

EPR thought experiment, hypothesis

I'm trying to understand the logic of the EPR thought experiment and what was the wrong hypothesis. Does the paradox appear because they applied the locality principle to an entangled state? But if we ...
user avatar
0 votes
0 answers
47 views

EPR Paradox and Density Operator

I am curious how one can use a density matrix in the following familiar cases in QM. 1. EPR Suppose a typical EPR situation where the state of a two-electron system is given by $\alpha|1\rangle|2\...
user avatar
7 votes
1 answer
401 views

How did the local hidden variable theory resolve the EPR paradox?

I'm trying to understand the motivation for local hidden variable theory. The EPR paradox considers the following thought experiment, where we can express a state $|\psi \rangle \in H_{Alice} \otimes ...
user avatar
0 votes
1 answer
57 views

EPR communication with double slit

I know this is probably not possible to use to communicate via EPR, so my question is why? I create electron entangled pairs using pair production or some other method, (each color pair is an ...
user avatar
3 votes
2 answers
230 views

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. ...
user avatar
  • 57
4 votes
4 answers
208 views

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 ...
user avatar
7 votes
3 answers
149 views

Has quantum collapse been ruled out?

This morning, a new arXiv paper 2105.13519 appeared providing detail of an EPR steering experiment showing that if it is assumed that the EPR steering requires quantum collapse, then more than one bit ...
user avatar
  • 11.8k
2 votes
1 answer
111 views

Where does the negative cosine relation for quantum mechanical CHSH correlations come from?

I have been lately looking into Bell's inequality. I have noticed a recurring graph that depicts the correlation of two spins when measured at different angles, for the quantum and the classical case: ...
user avatar
  • 127
4 votes
4 answers
755 views

How is superdeterminism a loophole to Bell's theorem?

I read wiki about superdeterminism and Bell's theorem and the lecture on free will, and I struggle to understand what free will has to do with the Bell's theorem. From my understanding, for Bell's ...
user avatar
  • 2,467
1 vote
2 answers
77 views

What does the output of the correlation look like in the typical experiments testing Bell inequalities when using light and polarizers?

I am curious to know what a plot of polarizer angle vs counts produces for experimental results of Bell tests vs the classical prediction.
user avatar
  • 306
1 vote
1 answer
97 views

Quantum eraser variant using a Stern-Gerlach magnetic field to direct the spin states of an electron towards one or the other of two slits

Consider a device consisting of a Stern-Gerlach apparatus (minus the detector screen), Hadamard gate, double-slit, and screen in sequence, tuned to direct electrons with spin up along a predetermined ...
user avatar
  • 3,681
-1 votes
1 answer
45 views

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 ...
user avatar
  • 415
4 votes
2 answers
199 views

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 ...
user avatar
  • 41
0 votes
1 answer
33 views

Implement EPR Imaging deconvolution

I have bruker's EPRI data and I want to deconvolute it. I read some article, that says $$ f(r) = x(r) \circledast g(r) \\ F(ω) = X(ω) \times G(ω) \\ X(ω) = \frac{F(ω)}{G(ω)} $$ $f(r)$: imaging spectre,...
user avatar
  • 1
3 votes
2 answers
183 views

When people say Bell's theorem implies either non-local realism or local non-realism, what do they mean precisely by "realism"?

From the EPR article: "If, without in any way disturbing a system, we can predict with certainty (i.e., with probability equal to unity) the value of a physical quantity, then there exists an ...
user avatar
  • 96
1 vote
0 answers
35 views

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 ...
user avatar
  • 121
0 votes
1 answer
119 views

EPR paradox and quantum entanglement

I have just been watching about EPR experiment on Leonard Susskind videos called entanglements and at the end of the 7 lecture he said that for say two particles of opposite spin up/down and at long ...
user avatar
4 votes
1 answer
107 views

Does an entangled pair remain entangled after the first measurement?

Consider an entangled pair described by the wavefunction $$\lvert1,0\rangle = \frac{1}{\sqrt{2}}(\lvert\uparrow_1\downarrow_2\rangle-\lvert\downarrow_1\uparrow_2\rangle)$$ in in the $S_z$-basis. If ...
user avatar
1 vote
1 answer
56 views

How the classical linear correlation of spin is derived?

I found this image on Wikipedia under Bell's theorem. I understand the blue curve generated by quantum mechanics, but couldn't understand how the classical curve (red curve) is generated (I don't ...
user avatar
1 vote
1 answer
55 views

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 ...
user avatar
  • 118
2 votes
1 answer
44 views

Conway's and Kochen's SPIN axiom seems unphysical

In their "Free will theorem", Conway's and Kochen's states the "SPIN axiom": "A triple experiment for the frame (x, y, z) always yields the outcomes 1, 0, 1 in some order.&...
user avatar
  • 23
0 votes
0 answers
167 views

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. ...
user avatar
  • 1
2 votes
0 answers
56 views

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 ...
user avatar
  • 173
1 vote
2 answers
182 views

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 ...
user avatar
1 vote
1 answer
155 views

If I start with an EPR pair and evolve one qubit through a unitary operation, what's really happening?

Suppose I have the EPR pair (maximally entangled state) as $|\phi\rangle$ and I apply an arbitrary matrix $U_3$ on the first qubit. $$U_3 = \displaystyle \left[\begin{matrix}\cos{\left(\frac{\theta}{...
user avatar
-1 votes
1 answer
58 views

Did the original EPR really consider an entangled state?

Or did only the subsequent thought experiments (Bohm & Aharonov, Bell) that introduced spin examine entangled states? The wikipedia article titled 'EPR paradox' claims as much: 'The thought ...
user avatar
1 vote
0 answers
55 views

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 ...
user avatar
  • 11
1 vote
1 answer
96 views

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 ...
user avatar
2 votes
0 answers
67 views

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 ...
user avatar
3 votes
0 answers
24 views

What (set of) angles are allowed between 3 detectors in the EPR experiment?

David Mermin's often cited popular example uses 60 degrees between 3 detectors which yielded what is said to be the maximum violation. Cosine 60 squared yields 25 percent which was below the ...
user avatar
0 votes
3 answers
214 views

Is the Bell's paper on the EPR paradox coherent?

I tried to read the Bell's paper on the EPR paradox but i rapidly stepped on difficulties : $$A(\vec{a}, \lambda) = \pm 1 ,\ B(\vec{b}, \lambda) = \pm 1 \tag{1}$$ So we identify $A$ with particle 1 ...
user avatar
0 votes
1 answer
95 views

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 ...
user avatar
1 vote
5 answers
323 views

Shouldn't classical physics force us to assume that there is determinism on a quantum scale?

I'm not a physicist, I have read a lot about Bell's theorem and the Einstein/Bohr debates and I have the following question: Judging by only classical physics, it seems we live in a 100% ...
user avatar
0 votes
2 answers
65 views

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. ...
user avatar
  • 103
-2 votes
4 answers
214 views

Moon paradox 2.0

Can anyone help me with what goes wrong with the following Moon paradox thought experiment ? You all know the faster than light (FTL) Moon "paradox": send a beam to the moon through a "hand laser," ...
user avatar
  • 267
1 vote
0 answers
29 views

EPR: How does measuring x_1 determine x_2 with certainty?

I am an undergraduate familiarizing myself with EPR for my upcoming bachelor's thesis, but this is probably pretty basic stuff for you out there. I am referring to the famous Einstein-Podolsky-Rosen ...
user avatar
2 votes
2 answers
185 views

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 ...
user avatar
2 votes
2 answers
46 views

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 ...
user avatar
0 votes
3 answers
129 views

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 ...
user avatar
  • 51
0 votes
1 answer
94 views

Sending Information With Entangled Particles

I learned from my quantum mechanics course that if you measure a quantum state twice, two things can happen: 1) You take the second measurement just after the first on. In this case, the result will ...
user avatar
0 votes
1 answer
183 views

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 ...
user avatar
0 votes
2 answers
112 views

Better Entanglement Explanation Required [duplicate]

It seems to me I have not read or understood a better explanation for quantum entanglement than Einstein's left and right glove explanation. If some Aspect (pun intended) of an entangled quantum ...
user avatar
0 votes
2 answers
118 views

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 ...
user avatar
  • 13
2 votes
1 answer
164 views

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 ...
user avatar
0 votes
1 answer
32 views

question regarding wikipedia page on pulsed electron paramagnetic resonance

Here, under the subtitle 'principle,' it describes what happens when you have a static magnetic field along the z axis, $ B_0 \hat{z}$ and microwave field parallel to the $x$ axis, $ B_1 \hat{x}$. I ...
user avatar
1 vote
3 answers
222 views

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 ...
user avatar