Tagged Questions

Quantum entanglement is the mechanism by which quantum correlations between two sub-systems survive even after being physically separated from an interaction region. The correlations could in principle survive without neither time nor space constraint.

learn more… | top users | synonyms

1
vote
0answers
15 views

Is it compulsory to solve the reduced density matrix

Is it compulsory to solve the reduced density matrix to get the eigenvalus for quantifing the von-Neumann entanglement entropy? Can't we proceed without those?
1
vote
0answers
41 views

Can any one solve this integral equation? [on hold]

I am presently working in the area "entanglement entropy". When i am trying to solve the integral equation $$\int_{-\infty}^{+\infty} dx_2' \rho_{2}(x_2, x_2') f_n(x_2') = p_n f_n(x_2)$$ for ...
1
vote
1answer
47 views

Entanglement Hamiltonian for two 1/2 spin system

Consider a two 1/2-spin state $$|\phi\rangle=\frac{1}{\sqrt{2}}(|1\rangle_A\otimes|1\rangle_B-|0\rangle_A\otimes|0\rangle_B),$$ cut in half (so we get A- and B-subsystem), the reduced density matrix ...
3
votes
4answers
109 views

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 ...
3
votes
1answer
84 views

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 ...
2
votes
1answer
36 views

What are the 'types' of parametric down conversion?

I'm looking at photon entanglement, and everywhere in the literature there's a reference to 'type-II' parametric down conversion as a source of entangled photon pairs. I know what parametric down ...
1
vote
1answer
87 views

Is it enough to use only sigma criterion to calculate expected value for ideal Bell's test experiment?

Let's build some custom distribution for particle measurement result in CHSH test. Let's assume ideal particles and detectors. Let's also assume that each particle has hidden parameter $z$. Parameter ...
1
vote
2answers
45 views

characterization of non-entangling gates

I suspect the following is true and "well-known" but I cannot find any reference for it. Can anyone help? Let $U$ be a unitary quantum gate acting on a pair of $d$-dimensional qudits. Suppose $U$ is ...
0
votes
1answer
43 views

Can two independent particles become entangled, or can they only be entangled at the time of their creation?

We were discussing this article at work, particularly the quote: “Finally, we can understand why a cup of coffee equilibrates in a room,” said Tony Short, a quantum physicist at Bristol. ...
3
votes
0answers
42 views

Entanglement g-2-experiment - Which 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 between ...
0
votes
1answer
55 views

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 ...
0
votes
2answers
52 views

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 ...
0
votes
1answer
51 views

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 ...
5
votes
0answers
104 views

Is there a way to obtain an RG flow equation for Quantum spin systems using MERA

We restrict ourselves to ground states of translationally invariant 1d quantum systems. I understand that there is the scale invariant MERA(multiscale entanglement renormalization ansatz) which ...
0
votes
0answers
32 views

Bell State Measurement From Parametric Down Conversion Source

My question is about whether or not there exists any scheme to distinguish between symmetric and antisymmetric Bell states from entangled pair of down converted photons. State of Down Converted ...
9
votes
1answer
139 views

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 ...
1
vote
3answers
295 views

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 ...
1
vote
2answers
75 views

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 ...
1
vote
0answers
35 views

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?
1
vote
1answer
61 views

Quantum Entanglement and BB84 protocol

Can Quantum entanglement can be used to strengthen the security or increase the efficiency of communication via the BB84 protocol? If so, how?
4
votes
1answer
152 views

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 ...
0
votes
0answers
48 views

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 ...
1
vote
2answers
141 views

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 ...
4
votes
2answers
92 views

Why would classical correlation in Bell's experiment be a linear function of angle?

Sorry if it's a newbie question, but I have trouble understanding the following part in the Wikipedia's explanation for the Bell's theorem: With the measurements oriented at intermediate angles ...
1
vote
1answer
39 views

Entangled Electrons

What attribute would help determine in a spaghetti of tangled-entangled electrons, which two are the respective entangled electron pairs, since obviously there is an attribute other than charge or ...
4
votes
2answers
75 views

2 entangled electrons in QFT

In field theory, by quantizing a dirac field, we can obtain a creation operator for a single electron of definite momentum, of definite spin up or down, these respectively are: ...
0
votes
2answers
84 views

Projection of Quantum State onto Bell State

I am very interested by this paper on entanglement swapping and timelike entanglement. The one thing I get really tripped up with is the whole idea of a projection onto a bell basis. I understand ...
0
votes
0answers
41 views

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 ...
3
votes
1answer
77 views

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 ...
5
votes
5answers
208 views

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 ...
1
vote
1answer
46 views

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 ...
8
votes
2answers
80 views

Natural entanglement system

I'm beginner and amateur interested by the quantum physics. I would like to know if it exists entanglements systems at natural state or it requires mandatory an human intervention ? Is it possible ? ...
4
votes
1answer
80 views

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), ...
6
votes
1answer
135 views

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 ...
0
votes
2answers
32 views

If I have created a polarization-entangled photon source, would I be able to create a qubit?

In my laboratory, I have already obtained a polarization-entangled photon source. It was created via the Spontaneous Parametric Downconversion process of 2 BBO crystals. The next question is that ...
3
votes
2answers
105 views

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 ...
2
votes
1answer
134 views

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 ...
-1
votes
1answer
85 views

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 ...
3
votes
0answers
133 views

Could the collision of two pairs of quantum entangled protons cause a temporary “wormhole”? [closed]

I recently read this article from MIT News. I then started thinking about how a particle accelerator creates a temporary microscopic black hole. My question is: If quantum entangled pair $A$, ...
0
votes
1answer
79 views

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 ...
2
votes
1answer
101 views

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.
0
votes
0answers
73 views

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 ...
3
votes
0answers
27 views

What are the requirements on conditional unitaries for overcomplete bases?

On way to describe "pure" decoherence (that is, decoherence with respect to a basis that doesn't involve transitions between basis states) between a system $\mathcal{S}$ and an environment ...
8
votes
2answers
164 views

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 ...
0
votes
0answers
46 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
0answers
261 views

How to understand the equivalence between Andreev reflection and Cooper pair injection?

It is well know that Andreev reflection dominates the subgap transport at the normal metal-superconductor interface. An incident electron can be reflected as a hole in the Nambu space, which ...
0
votes
0answers
48 views

Could the space outside the observable universe be entangled?

The title really says it all. One follow-up question is: How could one falsify this?
0
votes
0answers
52 views

Quick question on degeneracy of harmonic oscillator states

I'm currently learning about symmetry between particles. For a simple case of two non-interacting particles at $x_1$ and $x_2$, we know that the wavefunction can be written as $\psi_{n_1, n_2} = ...
2
votes
2answers
90 views

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 ...
1
vote
0answers
107 views

Beginner Quantum Mechanics Questions and Theories [closed]

So, I recently read the following article: http://www.preposterousuniverse.com/eternitytohere/quantum/ and I have some questions on some of the things it discussed, as well as some theories of my ...