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

6
votes
3answers
6k views

What is coherence in quantum mechanics?

What are coherence and quantum entanglement? Does it mean that two particles are the same? I read this in a book called Physics of the Impossible by Michio Kaku. He says that two particles behave in ...
1
vote
1answer
54 views

Quantum non-locality with commuting measurements?

We consider the Bell scenario, in which Alice and Bob share an entangled pure quantum state $\mid \Psi \rangle_{AB}$. Alice gets an input in the set $\{1,2\ldots X\}$ and Bob gets an input in the set ...
8
votes
4answers
5k views

How do particles become entangled?

A person asked me this and I'm just a lowly physical chemist. I used a classical analogy (how good or bad is this and how to fix?) Basically, light has a net angular momentum of zero, insofar as ...
4
votes
1answer
70 views

What are the phenomena responsible for irreversible increase in entropy?

https://www.quantamagazine.org/20140416-times-arrow-traced-to-quantum-source This article says that entanglement drives the arrow of time of increasing entropy towards thermodynamic equilibrium: ...
3
votes
2answers
121 views

When does the world split in MWI

I've been reading Eliezer Yudkowsky's blog post regarding decoherence and many worlds, and although he is not a physics but a strong proponent of MWI, I can basically see why he feels that MWI is a "...
1
vote
3answers
111 views

Precedence and quantum entanglement: The Alain Aspect experiment in spacetime

Recall that the spin components of a spin-entangled pair do not exist until one of the pair undergoes quantum observation, at which time both of the pair immediately obtain quantum random opposing ...
6
votes
1answer
61 views

If all the particles of a Bose-Einstein condensate become entangled with each other,does the system still remain a Bose-Einstein condensate?

I know that an entangled system is found in a single entangled state and that when you try to observe the individual state of a particle from an entangled system using a reduced density matrix, you ...
1
vote
0answers
24 views

The big bang singularity and entanglement [duplicate]

Since our universe began as a singularity would that mean that everything in the universe is entangled with itself? I am not sure that makes sense, but hopefully some one can figure out what I am ...
0
votes
1answer
64 views

If I pass one member of an entangled pair through a polarizer, does the other member assume a correlated polarization?

Does that mean I have influenced the measurement result of one member of the entangled pair by acting on the other? Can information be sent this way using entanglement?
0
votes
1answer
102 views

Replica trick for calculating Entanglement Entropy?

This is probably a simple question. Von Neumann entropy is defined to be $$S_A=-tr_A\rho_A \log\rho_A$$. And it's said that it can be calculate from the "Replica trick": $$S_A=\lim_{n\to 1}\frac{tr_A \...
0
votes
1answer
62 views

Would a collection of entangled particles behave like a superfluid? [closed]

Superfluidity of a Bose-Einstein condensate comes from the fact that all the particles are found in the same quantum state. They are described by the same macroscopic wavefunction. They never collide ...
0
votes
0answers
36 views

Why doesn't time dilation resolve entanglement

I'm a layperson who has read bits about relativity and quantum mechanics over the years, so this is a naive question, but I can't see where My reasoning fails... Photons travel at the speed of light, ...
1
vote
2answers
149 views

Quantum Erasure Spookiness

First off - I am not an expert. I am intrigued by quantum physics and have a layman's understanding at best. I've looked at other questions, but either the answers are not answering my question, or ...
-4
votes
1answer
812 views

Can quantum entanglement be a proof of a 4th spatial dimension?

What I know about quantum entanglement is almost nothing. What I know can be resumed to: "two particles created together have a correlated behaviour no matter the distance between them". This is ...
0
votes
1answer
33 views

On $k$-extendability of bipartite states

Definition of $k$-extendability can be given as follows. Let $k\in \mathbb{N}$. A state $\rho_{AB}$ on a bipartite Hilbert space $\mathrm{A}\otimes\mathrm{B}$ is $k$-extendible with respect to ...
4
votes
1answer
75 views

Basic Quantum Entanglement

Quantum entanglement means that multiple particles are linked together in a way such that the measurement of one particle's quantum state determines the possible quantum states of the other particles. ...
2
votes
1answer
122 views

What are the current obstacles to experimentally testing quantum pseudo telepathy?

Quantum pseudo-telepathy refers to how, in some specific coordination games, isolated players can do better when they have pre-shared some entangled qubits. I understand how it works in theory and ...
1
vote
0answers
17 views

Will efficiency of SPDC to create entangled photon increase with resonance?

If I put a non linear crystal inside a resonant cavity will efficiency of SPDC process to create entangled photon pair increase? If so by how much? Is there any experimental data? I have this paper ...
1
vote
1answer
88 views

Entanglement using a beam splitter?

Can someone explain why splitting light using a beam splitter is an example of entanglement? I get the part where we cannot definitively tell which photos have gone in which direction, but i thought ...
6
votes
3answers
1k views

Pauli exclusion principle and Entangled pairs

It is true for fermions in the same potential that the total wavefunction of two particles must be antisymmetric with respect to exchange of electrons. Which means the spin wavefunction is given by $...
2
votes
2answers
50 views

Can decoherence occur just by simple reflection?

I create an entangled photon pair. One photon is sent inside a resonant cavity which reflects the photon many number of times. Will there be decoherence between photon in the resonant cavity and its ...
3
votes
2answers
286 views

mixture of maximally mixed and maximally entangled state

Consider the quantum system $\mathcal{B}(\mathbb{C}^d\otimes\mathbb{C}^d)$ and $|\psi\rangle=\frac{1}{\sqrt{d}}\sum_{i=0}^{d-1}|i,i\rangle$ be the (standard) maximally entangled state. Consider the ...
16
votes
7answers
2k views

Quantum entanglement vs classical analogy

Consider that we have two balls, one white and one black, and two distant observers A and B with closed eyes. We give the first ball to the observer A and the second ball to the observer B. The ...
3
votes
2answers
144 views

Conservation of quantum coherence?

Is coherence conserved under unitary transformation? As we saw in the process of generating entanglement, coherence between states of the subsystem is transferred to quantum correlations (related to ...
0
votes
0answers
26 views

Optical Parametric Amplifier performance compared to Optical Parametric Oscillator

I am trying to design a bright source of polarization entangled beams of photons so that it is visible to human eye. I have to decide between OPA and OPO. OPAs are cheap and simple to develop compared ...
4
votes
1answer
62 views

Entanglement for Gaussian states

Let us consider the product Fock space $\Gamma(\mathbb{C}^m) \otimes \Gamma(\mathbb{C}^n)$ and consider Gaussian states in that space. While reading some literature on Gaussian state entanglement (...
66
votes
10answers
8k views

Quantum Entanglement - What's the big deal?

Bearing in mind I am a layman - with no background in physics - please could someone explain what the "big deal" is with quantum entanglement? I used to think I understood it - that 2 particles, say ...
-1
votes
2answers
176 views

What stands behind the quantum nonlocality appearing in entanglements, and why Bell's inequalities are violated?

I noticed the question whether Bell's inequalities are based on a false premise, (Could Bell's Theorem be based on a false premise?) but I bring another argumentation of the question. Also I ...
0
votes
1answer
166 views

Quantum Measurement of Entangled Time-Varying Systems

Suppose System A has a dynamic, continuous variable $O_A(t)$, which we wish to measure via a quantum probe. Assume system A has a self-Hmiltonian, $H_{SA}$ so that the evolving wave function of ...
35
votes
0answers
1k views

Orbits of maximally entangled mixed states

It is well known (Please, see for example Geometry of quantum states by Bengtsson and Życzkowski ) that the set of $N$-dimensional density matrices is stratified by the adjoint action of $U(N)$, where ...
0
votes
1answer
39 views

Does the Delayed Choice Quantum Eraser require the signal and idler photons to be entangled?

In everything I've read about the Delayed Choice Quantum Eraser Experiment, the descriptions talk about the BBO crystal splitting of the photon into two entangled parts. The signal photon of the pair ...
1
vote
0answers
54 views

Entanglement in laser beams [closed]

Recent experiments in entanglement of two laser beams using OPOs indicates higher level (photon group instead of pair) of entanglement. When a higher ensemble of photons are entangled there is no ...
0
votes
2answers
61 views

On significance of Quantum Entanglement

I'm a Software engineering bachelor student and hence i don't have a strong physical background. i've been recently studying material related to quantum computing and its underlying physics and i came ...
2
votes
1answer
68 views

Quantum teleportation of atomic states that involve energy [duplicate]

With quantum computing the concern is with information, and when quantum teleportation appears, the states being transferred are often spin states. However, there is an energy difference, even if ...
2
votes
2answers
122 views

Why when we have GHZ, then we cannot send a qubit using teleportation technique? [closed]

Suppose the following example Alice has a qubit $|A\rangle$ and Bob has a qubit $|B\rangle$, then by teleportation technique we can send an unknown qubit state (i.e. $|\psi\rangle = \alpha |0\rangle ...
1
vote
0answers
47 views

Converting a Bell state to a less entangled state by LOCC [closed]

How can I convert a maximally entangled state, $ \frac {1} {\sqrt2} (|00\rangle +|11\rangle) $, to a less entangled state like, $$ cos(\theta)|u_0 v_0\rangle + sin(\theta)|u_1 v_1\rangle $$, by using ...
0
votes
0answers
44 views

Why does the interference patterns in delayed choice quantum eraser cancel out? Why/how does it have a phase shift?

Talking about this experiment https://en.wikipedia.org/wiki/Delayed_choice_quantum_eraser#The_experiment_of_Kim_et_al._.282000.29 I am assuming that anyone able to answer my question is already ...
1
vote
1answer
217 views

Single quantum particle in beam splitter, with different systems located in each channel

Suppose a quantum mechanical particle enters a beam-splitter, which sends its wave packets into two mutually orthogonal channels, $C_a$ and $C_b$. Suppose that $C_a$ also contains System A, with ...
7
votes
6answers
536 views

Can quantum entanglement be simulated on a digital computer to any degree of precision?

First principles modelling of physical phenomena has been very successful in physics. The largest limitation is perhaps the fact that many QM problems are NP hard so we would need really powerful ...
1
vote
0answers
107 views

The link between non-locality and Heisenberg's uncertainty relations

I have recently found out1 that the concepts of non-locality and Heisenberg's uncertainty do not live independently of one another in Quantum Mechanics. In other words, roughly the idea goes as: the ...
0
votes
3answers
186 views

Quantum entanglement - problem with Bell's inequality [closed]

To ask the question, I will state the scenario first. Please let me know if the scenario is not described appropriately. The question is in the scenario itself. There are many questions marks in this ...
3
votes
2answers
336 views

quantum entanglement at microwave frequencies

Entanglement of optical photons using non-linear crystals has been around for a long time. Macroscopic entanglement using diamonds recently reported in the literature and receiving considerable ...
0
votes
1answer
53 views

Quantum Entanglement of Lee and Ron [duplicate]

Lee and Ron are born as perfectly identical twins except for Lee being left handed and Ron being right handed. Years after birth they are seperated, Lee moving to Latvia and Ron moving to Rwanda. At ...
9
votes
3answers
6k views

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 ...
4
votes
1answer
85 views

A question about the universal quantum cloning machine (UQCM)

In the recent paper Replicating the benefits of Deutschian closed timelike curves without breaking causality, a quantum state cloner based on open timelike curve (OTC) was mentioned. There to clone ...
0
votes
2answers
93 views

Does quantum entangled particle release energy when its “twin” is measured? [closed]

So I was just thinking a bit, and I came up with a couple of questions. As we all know the scenario: We have two quantum entangled particles. Let's call them A and B. We like to measure the state of ...
3
votes
1answer
86 views
0
votes
0answers
34 views

Entanglement up to a finite distance

We do not have a theory which predicts the working distance of entanglement, and this distance is usually taken to be infinity. However, up to now, experiments have just rigorously confirmed ...
4
votes
5answers
501 views

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 ...
2
votes
1answer
82 views

Entanglement, superposition, and propositional logic [duplicate]

From what I am understanding, there is entanglement in a system if there is a correlation between elements of that system. For an example that I found, If you have only two cards and know that one is ...