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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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Could reducing entanglement by unitary operations allow for FTL-communication? (and why not?)

About the closure: This Question is about why manipulating 1 particle of an entangled pair unitarily can’t cause measurable consequences on the other and how this manifests in the concretely described ...
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How do physicists talk about spin of individual particles when the universe is massively entangled?

The following two things seem to be true: (1) The universe is massively entangled because the wave function that describes the entire universe has measure 1 of being entangled. Further, given how ...
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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 ...
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Precise formulation of the ER = EPR conjecture

Maldacena and Susskind have "formulated" the now famous ER = EPR conjecture in their paper Cool horizons for entangled black holes, but as of today, I have not find a quantum theorist who ...
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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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Two-mode squeezing and EPR

Consider the two-mode squeezing operator $S(\xi)=\exp\left(\xi\hat{a}^{\dagger}\hat{b}^{\dagger}-\xi^*\hat{a}\hat{b} \right)$ with $\xi=r\exp(\text{i}\phi)$, and assume that the initial state of the ...
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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 ...
Masato Morifuji's user avatar
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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 ...
Hari Kumar's user avatar
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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 ...
Hari Kumar's user avatar
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1 answer
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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 ...
Hari Kumar's user avatar
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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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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 ...
Mikayla Eckel Cifrese's user avatar
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1 answer
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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 ...
Lory's user avatar
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On Bohr's response to EPR

If I understand correctly, the EPR paper (1935) points out that quantum mechanics is incomplete theory if it describes individual particles and measurements. This is true by the mathematical formalism....
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Quantum entanglement Bell's inequality and Nobel prize [closed]

Just your average layman here, wanting to understand the whole entanglement work for the Nobel prize. Why can't the entangled pairs have a fixed spin that we don't know? How do experiments prove ...
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EPR measurement + local unitary operation

Consider an EPR pair $\frac{1}{\sqrt2}\left( |\uparrow \rangle_A \otimes |\downarrow \rangle_B - | \downarrow \rangle_A \otimes | \uparrow \rangle_B \right)$ and the standard conventions (notation) ...
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Are Bell's inequality and CHSH inequality the same?

Are Bell's inequality and CHSH inequality different? I tried to read about them and I understood that both disprove local hidden variable theory but I do not understand how they are different(if they ...
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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?
TheDiracEquation's user avatar
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Question about Bell's 1964 paper and its Illustration section [duplicate]

I have been trying to understand the maths behind the original paper on the EPR paradox, and I understand most of the details within it, in particular the main argument. However it is in the third ...
ar.row's user avatar
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Is there any interpretation where GR and QM can be compatible?

In this article [1] , Dr. Sten Odenwald claimed that, Quantum mechanics is incompatible with general relativity because in quantum field theory, forces act locally through the exchange of well-...
Sazzad Hissain Khan's user avatar
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2 answers
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Are the inequalities from Bell's Theorem ever actually satisfied?

Following Griffiths's description from Introduction to Quantum Mechanics, Bell's original experiment was based on the EPR-Bohm experiment, where one considers the decay of a neutral pi meson into an ...
Stephen Fedele's user avatar
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Why can't we say that the information is travelling faster than light? [duplicate]

Let's imagine the following thought experiment, Two particles, A and B are entangled on the Earth. As decided, Alice (a friend of Bob) stays on the Earth with the A and Bob travels with the B to a ...
Sazzad Hissain Khan's user avatar
1 vote
1 answer
154 views

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 ...
Sazzad Hissain Khan's user avatar
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1 answer
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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 =\...
Solidification's user avatar
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How to disentangle two entagled particles (photons) without distroying anyone?

Can a twin photon pair entagled in polarization get disentangled after one of the photons meets a PBS (polarization beam splitter). I suppose after the PBS the photon will go one way or another ...
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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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An input-output explanation of a quantum photonic setting

I am a computer scientist specialising in quantum information processing. I am currently struggling to understand the photonic setting in the figure below (coming from this paper). I wonder how a ...
Daniele Cuomo's user avatar
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1 answer
212 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 ...
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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 ...
Srinivas N Rao's user avatar
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1 answer
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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 ...
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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 $|1\rangle$ ...
Lory's user avatar
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1 answer
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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 ...
Display name's user avatar
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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\...
Lory's user avatar
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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 ...
user135520's user avatar
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3 answers
235 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 ...
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2 answers
795 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. ...
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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 ...
Emanuele Giordano's user avatar
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3 answers
177 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 ...
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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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6 answers
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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.
barry's user avatar
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1 answer
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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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3 answers
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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,...
mikie's user avatar
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3 votes
2 answers
471 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 ...
A.D.'s user avatar
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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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4 votes
1 answer
180 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 ...
Solidification's user avatar
1 vote
1 answer
99 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 ...
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