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

2
votes
2answers
140 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
57 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 ...
-2
votes
2answers
172 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
165 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
979 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
38 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
58 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
65 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
116 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 ...
-2
votes
1answer
101 views

Why is particle superposition still part of quantum mechanics? [duplicate]

After reading an article on Schrodinger's Cat, it seems that if we take the environment as an observer, that superposition cannot occur because all atomic and subatomic entities would be observed all ...
1
vote
0answers
46 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
215 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
516 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
106 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
177 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
330 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
51 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 ...
8
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
79 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
92 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
85 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
499 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
79 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 ...
1
vote
3answers
77 views

Is it probable for particles to become entangled under natural conditions?

Under what circumstances could particles become entangled without our intervention? How frequent would that have happened in the various stages of cosmic expansion? Is it possible that particles may ...
1
vote
0answers
36 views

Why is entanglement such a big deal? [duplicate]

I just learned about it to some depth (not very much, just the basics), and I fail to see why is this phenomenon considered strange or unexpected and the like at all. I mean let's consider a bag with ...
2
votes
2answers
147 views

What patterns could be observed in this quantum entanglement thought experiment?

Please see attached image below. The DEVICE is beaming two streams of entangled particle pairs (B1 and B2) in opposite directions (e.g.: Particle no. 1 (p1) goes left, Particle no. 2 (p2) goes ...
0
votes
0answers
43 views

A New Approach to Quantum Entanglement Communication [duplicate]

I've read other posts on the feasibility of quantum entanglement as a means of communication so I'll save repeating what's already been said. Typically it seems to be shut down as an option because ...
3
votes
2answers
68 views

Entangle more than two atoms?

Alright so we know that we can entangle any two atoms, however, what exactly is stopping us from entangling more? In theory, shouldn't we be able to entangle a third to the already entangled pair? ...
4
votes
1answer
76 views

Is it possible to make a state tomography of an entangled state only by measurements on subsystems?

As far as I can understand, to make a state tomography of a composite system, a properly selected set of joint measurements should be carried out on the composite system to estimate the density matrix ...
1
vote
1answer
104 views

How to understand the measurement on entangled state in the following cases? [closed]

Assuming an EPR pair AB, event MA is a measurement on A. My questions are: (1) At MB and MB' (depending on where B is located), if we try to describe the state of B (but not measure B yet), ...
2
votes
1answer
97 views

What's wrong with my Quantum Early Warning System (Thought Experiment) [closed]

I'm a lay physics enthusiast and I came up with a thought experiment that I can't fully wrap my head around: Alice and Bob are worried about an impending attack by the dreaded Xenomorphs, so they ...
1
vote
0answers
37 views

Modified double slit experiment with single entangled particle [closed]

Say we use one of the entangled particle (A) for the experiment, if we measure the other particle (B) would particle (A) still be able to exhibit interference pattern since physically only the ...
1
vote
0answers
37 views

Quantum entangled particles [closed]

Do we understand why particles are paired with specific other ones? Were they born together or existed right next to one another at another time? Can they pick (entangle) with new ones? Do we have ...
2
votes
0answers
45 views

How does gravity affect entanglement?

Hypothetically an entangled pair of atoms are placed inside two similar satellites orbiting at the same altitude, one of the satellite will then slow its speed and descend towards the surface of ...
0
votes
1answer
163 views

How does measurement affect multi-particle entangled particles?

It is my understanding that you can have two entangled particles, A and B, and measure their spins from two different angles, X and Y, such that: If you measure A using one angle (e.g. X), there's ...
3
votes
3answers
602 views

Entanglement and the double slit experiment

Is the double slit experiment an example of entanglement when it seems as if the photon is going through both slits? Or put another way, is it at this stage when we attempt measurement we see a photon ...
2
votes
3answers
639 views

Faster than light signals and the price to be paid if we accept them : a very simple protocol

Some physicists currently understand entanglement as transferring information instantaneously, yet not violating causality. Is this really a satisfactory explanation, or should be look for something ...
9
votes
2answers
142 views

Natural entanglement system

I'm a beginner and amateur interested in quantum physics. I would like to know if entangled systems of natural states exist or whether such systems require human intervention? Is it possible? Either ...
4
votes
1answer
66 views

entanglement of different types of particles possible?

Perhaps this question makes no sense physically, but is it theoretically possible to entangle a photon with an electron, for example? I know that entanglement links a specific property of particles, ...
4
votes
4answers
1k 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 ...
8
votes
1answer
142 views

Entanglement and the Pauli exclusion priciple

Could you say that two electrons in the ground state of a helium atom experience quantum entanglement? They are both in the same energy level and cannot have the same quantum numbers. If one is spin ...
1
vote
3answers
114 views

What is wrong with this method for FTL communication? [duplicate]

I've seen the other questions, but almost all of them deal with manipulating quantum states so that the other person reads a message in the data. However, you cannot force a quantum state on ...
3
votes
1answer
58 views

Quantum entanglement and superdense encoding etc

Is the following a somewhat correct analogy for what these phenomenae are? Imagine a box of thousands of apples where exactly half of each apple is red and the other half is green. Each apple is ...
1
vote
2answers
1k views

can we transfer data via quantum entanglement (likewise we communicate today) to a specific target

Today we rely on electromagnetic field for communication. I'm a entrepreneur, I want to know why we can't transfer data with this technology to transfer data from one place to another place. It can ...
12
votes
1answer
522 views

Quantum computing records (entangled qubits)

What is the current record number of entagled qubits and how has this number been increased? The latest result on stack exchange, which is 3 years old, reports 14 via this post: How many stabilised ...