All Questions
Tagged with quantum-mechanics quantum-entanglement
1,353 questions
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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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1
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Do entangled particles lose entanglement after polarizing filters?
If two entangled particles are sent through different polarizing filters, do they lose their entanglement after the filters?
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Can Quantum Entanglement and Quantum Superposition be considered the same phenomenon?
Quantum entanglement is known to be the exchange of quantum information between two particles at a distance, while quantum superposition is known to be the uncertainty of a particle (or particles) ...
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4
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Is this an entangled state?
Is the following state entangled?
$\left| \psi \right> = \alpha_0 \beta_0 \left| 00 \right> + \alpha_0 \beta_1 \left| 01 \right> + 0 \left| 10 \right>+ \alpha_1 \beta_1 \left| 11 \right&...
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What is the difference between correlation and entanglement?
I have read that not all correlated states are entangled. What is the difference between the two?
Mathematically, it was stated that a system which can be put in the form of
$\sum_{k}p_{k}\hat{\rho}...
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2
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Entanglement $g^{(2)}$ experiment - what components do I need?
I would like to measure whether my source emits entangled photon pairs. To that order I want to build a $g^{(2)}$ experiment, which measures photon coincidence counts as a function of time delay ...
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2
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529
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Does a normal torch emit entangled photons?
I was reading a sciencenews.org post about three photons being entangled. My question here is, why is the chance of producing an entangled pair once in a billion times? Isn't every particle produced ...
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Does a random local unitary destroy entanglement
There is a massive debate raging about whether the wavefunction is an aspect of reality or just a way of handling the data you have about a system. This question is in that vein.
A local unitary on ...
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How to find optical toy models of entangled quantum mechanical systems?
I recently read Arnold Neumaier's lectures on uncovering classical aspects of quantum mechanics:
Classical and quantum field aspects of light
Optical models for quantum mechanics
I can't find the ...
2
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1
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Can entanglements themselves be entangled?
In other words, could there be higher dimensional entanglements between entanglements? For instance, this could allow us to entangle two entangled-far-away pairs to create a system of four entangled ...
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Why is the dimension of the set separable states $\dim\mathcal H_1+\dim\mathcal H_2$?
Please can you help me to understand how the dimension of the set of separable states is $\dim \cal H_1 + \dim \cal H_2$?
This is the relevant passage:
So far, we have assumed implicitly that the ...
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How to tell whether photons are entangled?
Suppose you have some sort of a "black box" system - you know nothing of its inner workings. The system has two outputs, let's call them A and B, and it occasionally emits photons - one photon from ...
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4
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Quantum Entanglement - an illusion based on a wrong assumption?
Almost all resources I've read about Quantum Entanglement speak about how 'amazing' it is that two entangled particles are bound over any distance, and that the state of one particle determines the ...
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2
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Quantum Eraser thought experiment with light photons of distinct color
I tried to recreate the Quantum Eraser experiment into a thought experiment with a few changes. It left me a little perplexed as to what outcomes I should expect. Any help would be appreciated.
Lets ...
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Entangled particles interaction with other particles
Non-physicist question:
Suppose two particles A and B are entangled and A collides with another particle. What happens to B?
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Is entangled state after measurement still an entangled state?
Suppose there is an entangled state of two electrons, the spin part is
$$| \downarrow \uparrow \rangle - | \uparrow \downarrow \rangle \tag{1} $$.
If I add the spatial part of the wavefunction as two ...
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Theoretically, is there a way to hold a quantum entangled particle in a state by continuously observing it?
When the spin of a quantum entangled particle is measured, is it only possible to do an instantaneous measurement, or can a particles spin be held in a collapsed state by constantly observing it?
In ...
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Why are results of Bell's experiments considered to "break realism"?
Related to my previous question (Why would classical correlation in Bell's experiment be a linear function of angle?), as a newbie in quantum mechanics, I am also unable to find the reason to why ...
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Non-unqiue basis sets of reduced density matrix in quantum mechanics/decoherence
In Why decoherence solves the measurement problem by Art Hobson:
$|\psi \rangle _{SA} = c_1|s_1 \rangle |a_1 \rangle + c_2 |s_2\rangle |a_2 \rangle$
which is a wavefunction that describes non-local ...
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Is this double "double slit experiment" involving entanglement possible?
The experiment goes as follows:
Put a particle emitter (photon, electron etc.) between a pair of double slits. The emitter launches pairs of particles that are entangled in such a way that if one ...
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6
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Quantum entanglement and spooky action at a distance
When quantum entanglement is explained in "layman's terms", it seems (to me) that the first premise, that we have to accept on faith, is that a particle doesn't have a certain property (the particle ...
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In quantum entanglement are the 2 sub atomic particles exhibiting all possible values before being measured
I have been reading a lot about quantum entanglement when I came up to a part which says that before measuring one of the particles there is a 50:50 chance that a particle will be one of the pair but ...
4
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Does first quantization perturbation theory imply a large scale web of electron entanglement?
My question may seem quite esoteric given the title, but I think it's relatively straightforward when explained properly. Imagine a relatively simple situation of 2 hydrogen atoms (numbered 1 and 2), ...
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What does this question about entanglement and classical geometry mean?
Below is the question from Andy Strominger's presentation at the String 2014 conference. The question was asked by credible physicist Ashoke Sen as an important question.
"What is the precise ...
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Is space-time a Kantian concept - just a concept of the working mind? [closed]
Is space time a Kantian concept – that is, just a concept of the mind at work? That is that there is no ‘out there’ – it’s in the ‘mind’?
Relativity might work but it certainly requires a stretch of ...
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How to explain in simple terms why Entanglement is more than just complicated hidden variables
I haven't taken a graduate level physics course on quantum mechanics so I get lost in the strange looking equasions.
It's hard for me too see in any of the explanations of how quantum computers and ...
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Quantum Mechanics and Entanglement
I'm hearing a guy ( Tom Cassidy ), which supposedly has a master in physics, saying that what we expect in a physical experiment ( for example, observing some particle ) can actually interefere with ...
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Can we use quantum entanglement as a way to send information or data? [duplicate]
Can we use entangled particles to transmit information or data such as TCP/UDP packets?
If so why hasn't this been done yet? Surely the costs of bringing this to market are much cheaper than laying ...
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Does quantum entanglement imply the existence of a non-causal structure connecting space-time together? [closed]
In contrast to a "time-like" or "causal" structure connecting space-time together, Does quantum entanglement imply the existence of a "space-like" or "non-causal" structure holding space-time together ...
3
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406
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What would happen if two entangled particles collided?
Does that is even possible? I have almost zero knowledge in quantum physics, it is just a curiosity that popped in my mind.
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663
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How does cryptochrome produce quantum entanglement?
I found this video on the net, which explains how a bird called "European robin" uses a trick based on quantum entanglement to see the earth's magnetic field. I am just asking if some of you know any ...
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University of Delft results regarding quantum teleportation of information
I have a college-level understanding of Physics. A recent study from the University of Delft in the Netherlands that seems to suggest that quantum teleportation of information (as in "communication of ...
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2
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Wouldn't 3 or more particle entanglement allow passing classical information?
My (simple) understanding of entanglement is that by measuring the spin of one entangled particle, the other entangled particles' spin changes to the opposite of measured particle. This act of ...
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Quantum entanglement and special relativity PARADOX [closed]
Imagine two entangled atomic clocks. After we entangle them, we measure the time: it does has to be the same , right ?
Now lets suppose that we entangle them , but don't measure them, then we plant ...
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EPR Experiments and Monogamy
Normally in an EPR experiment two measurements are performed on entangled particle pair. Only the particle pair is treated quantum mechanically and it is usually prepared in a state like
$$ (\,\left|\...
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6
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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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How does one produce entanglement?
In practice, when entangling two particles (say two electrons), is creating an entangled state purely a matter of bringing them close enough together? What I mean is, to make their wave functions ...
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1
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How do we know quantum entanglement exists/happens? [closed]
We know that this strange behavior is there but I am not to able grasp, how do we know it exists? Have we ever tried any experiments confirming this? Do we make use of this?
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What happens when an electron jumps through the event horizon of a black hole?
If quantum teleportation is performed into a black hole (by an electron for example), what happens to that electron?
Let's say a hydrogen atom is very close to a black hole and the electron jumps ...
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Why can't I use Bell's Theorem for faster than light communication?
I read this description of Bell's theorem. I understand he's restating it slightly, so there may be incorrect assumptions there, or I may have some. I think Bell's theorem should lead to FTL ...
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2
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wave-particle duality and entanglement
By fundamental definition of a entangled system we can say that if we know the quantum state of one subsystem then we can describe the state of another subsystem.
A particle possess wave-particle ...
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How could there be a truly "pure" state?
If the Universe did start from a single point, then wouldn't all particles be fundamentally entangled? How then could there be a truly "pure" state?
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Quantum entaglement and the arrow of time
I have seen several claims to that quantum mechanics is required to explain the arrow of time which I take to mean the macroscopic irreversibility of physical systems. This is presumably to resolve ...
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Quantum entanglement on cosmological scales
This may be a foolish question given my limited understanding of QM but here it is.
As I understand quantum entanglement basically means that two particles evolve as a single "unit", i.e., are ...
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What is meant by a quantum factoring for entangled states?
The definition of an entangled state $|\Psi\rangle$ is that it CANNOT be factored into
$$|\Psi\rangle=|\psi\rangle_1\otimes|\phi\rangle_2$$
I am kind of confused on what is meant by a quantum ...
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Quantum entanglement: does it necessarily imply superluminal information transfer? [duplicate]
From what I understand, information is communicated instantly between two quantum-entangled particles regardless of the spatial distance between them. However, does this necessarily imply superluminal ...
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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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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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3
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Entanglement in single particle state
Is it possible that we have entanglement in different degrees of freedom of a single particle, like spin and linear momentum?
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Particle/antiparticle annihilation and entanglement
This is a basic question. Suppose that A and B are completely entangled particles and so are C and D. If B and C are antiparticles that annihilate each other will A and D be entangled as a result. It ...
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