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.

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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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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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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 ...
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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: ...
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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 ...
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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.
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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 ...
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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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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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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,...
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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 ...
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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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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 ...
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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 ...
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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 ...
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45 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 ...
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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.&...
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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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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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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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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}{...
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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 ...
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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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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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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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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 ...
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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 ...
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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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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% ...
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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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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," ...
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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 ...
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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 ...
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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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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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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 ...
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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 ...
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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 ...
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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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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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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 ...
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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 ...
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When does the wave function collapse in the EPR paradox experiment? Shouldn't this depend on the reference frame?

Suppose you have two entangled particles. Particle A, and Particle B. If the spin of particle A is up, then the spin of particle B must be down and vice versa. Now suppose you measure the spin of A ...
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Distinguish Definitions: Realism Scientific, Realism, and realistic

I was readying about study about bell's theorem, where I had the question about some definitions. Here's some of my summaries: Scientific Realism: (https://en.wikipedia.org/wiki/Scientific_realism#...
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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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What's the invariance quantity under EPR and Bell's inequality?

I was reading and writing a study report about EPR and Bell's inequality. As the hidden variable and local realism was proven to be "false", and from many posts in physics exchange websites such as ...
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Are properties such as locality and realism properties of all theories, some theories, or interpretations of theories?

I have a strong intuitive feeling, based for example on the Bothe-Geiger experiment, that quantum mechanics is nonlocal. But intelligent people who have thought about these things make claims such as ...
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From locality to deterministic hidden variables

According to this link here Bell said: "My own first paper on this subject ... starts with a summary of the EPR argument from locality to deterministic hidden variables. But the commentators have ...
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EPR experiment with photons

In textbooks, the EPR problem and Bell's Inequality are dealt with for particles. However, when it comes to experimental verification, photons are used. The formula for the expectation value for ...
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Completeness of quantum mechanics and the EPR paradox

I am reading through the EPR paper and follow most of it. The authors argue that either QM must be incomplete (let's call this statement A), or incompatible observables can not have simultaneous ...