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

4
votes
2answers
151 views

Delayed Choice Quantum Eraser: Am I missing something here?

Hello everyone, I actually have three questions: Am I missing an important detail in my understanding of how the delayed choice quantum eraser experiment is done? How does one account for what ...
-1
votes
1answer
52 views

Checking correctness of partial trace

I am doing some simulations that requires me to take partial trace over a three qubit density matrix $\rho_{ABC}$. I find the mixed state density matrix of one qubit by tracing out the other two, ...
2
votes
1answer
52 views

Local operation on bipartite quantum system [closed]

Suppose we have a state: $$ |\Psi_{1234}\rangle = \frac{1}{2}\left(|\Psi_{14}^+\rangle \otimes |\Psi_{23}^+ \rangle + |\Psi_{14}^-\rangle \otimes |\Psi_{23}^- \rangle - |\Phi_{14}^+\rangle \otimes ...
-1
votes
1answer
36 views

Correlated bell states

I have a question about terminology. What is the terminology for describing 2 correlated bell states shared by 4 qubits?
0
votes
0answers
32 views

Entanglement swapping and Bell state analyzer

In entanglement swapping where AB from two entangled pairs AC and BD are projected into Bell state by Bell state measurement (https://en.wikipedia.org/wiki/Bell_state#Bell_state_measurement) on A and ...
0
votes
1answer
32 views

Question about Bell state analyzers

Is there a Bell state analyzer that would take as input 2 qubits in Bell state, distinguish between psi and phi states and send psi states to output A and phi states to output B?
0
votes
1answer
22 views

Discriminate between bell states

Is it possible to discriminate between 2 of the four Bell states (phi, psi) and does it interfere with the entanglement?
0
votes
1answer
64 views

Need help understanding delayed choice and entanglement swapping

From delayed choice experiment The results of all four measurements are then compared. If Victor did not entangle his two photons, the photons received by Alice and Bob are uncorrelated with ...
0
votes
0answers
21 views

Interferometric Entanglement of path and spin

I am looking at a problem where I can have a spin 1/2 particle in either a |1$\rangle$ or a $|0\rangle$ state in an interferometer (0 is one arm and 1 is the other). And the spin 1/2 follows the ...
1
vote
3answers
60 views

Size of Objects in entanglement

Pardon the possible obviousness of my lack of understanding entanglement but how big have we noticed the objects in the system whole? We talking particles or can planets or universes be entangled? ...
1
vote
1answer
43 views

Does entanglement entropy remain constant?

So I am trying to figure out what the time derivative of entanglement entropy is $$\frac{d}{dt}(-Tr[\rho^A\log_2\rho^A])$$ Where $$\rho^A=\sum_{aa'}|a\rangle\langle a'|\sum_bc_{ab}c_{a'b}^*$$ And ...
0
votes
1answer
90 views

Quantum entanglement and information transfer

I know it was stated many times that information transfer using entanglement is not possible and I am most probably wrong but I would be glad if you can at least point me to where I am mistaken. If ...
1
vote
1answer
24 views

Quantum entanglement continuous measurement

Is there a possibility (if not real than at least theoretical) that we could measure the spin of an electron continously over some (even very short) period of time, so that it does not change during ...
2
votes
1answer
67 views

Is physical contact necessary for entanglement

My question is as follows: Is it absolutely necessary for particles to come into contact before they can be entangled? Has any experiment reported of particles which were never in contact showing ...
-2
votes
1answer
77 views

Popular books on cutting-edge physics [closed]

I watched this video, in which different types of topics are discussed like Quantum Information, Quantum Computation, Universe as hologram, Hidden information, Quantum Entanglement, Black holes and ...
-2
votes
1answer
58 views

Quantum entanglement correlations [closed]

I have a vague idea of what entanglement is but I am stuck at one place: we all know that entanglement is destroyed with time. this is called decoherence. I wish to know if there is any correlation ...
3
votes
1answer
49 views

When can a Hilbert space with a given Hamiltonian be decomposed into non-interacting tensor product factors?

Let's say I have a Hilbert space $\mathcal{H}$ (either finite-dimensional or with a countably infinite basis) with a specified Hamiltonian $\hat{H}$, representing some quantum system. Under what ...
2
votes
2answers
74 views

Why can't be the EPR experiment simplified?

Alice measures the spin of her electron on the x axis. She now knows the spin value of Bob's electron on the x axis at time T0. Bob measures the spin of his electron on the z axis. He now knows the ...
6
votes
1answer
84 views

Indirect probing of entanglement measures

Entanglement is a purely quantum mechanical phenomena that e.q. increase precision of quantum interferometers, atomic clocks or have application in quantum computing. There are many "measures" of ...
1
vote
1answer
102 views

Separability of density operators on tensor product spaces

Consider a composite system $\mathcal{H}=\mathcal{H}_{A}\otimes\mathcal{H}_{B}$ where $\mathcal{H}_{A}$ and $\mathcal{H}_{B}$ are Hilbert spaces of constituent components (say two qubits). Let ...
1
vote
1answer
83 views

Why would hidden variables in Bell's Stern-Gerlach experiment related to entanglement require only 4/9ths of the measurements to be equal?

Bell's Stern-Gerlach experiment, consisting of 2 sets of detectors each with 3 randomly chosen detection directions, is one of the most important experiments cited as proving that entanglement has ...
0
votes
1answer
55 views

Speed of entangled particle changes [duplicate]

If two particles are entangled at a distance of light years, does changing one affect the other instantaneously, or does it take years to occur? What gives us the answer to this question?
0
votes
1answer
77 views

How to discern that a subsystem of entangled system is in a mixed state

We have a an entangled system, composed of two subsystems, $A$ and $B$, in a pure state $|\Psi\rangle$, in a basis $|ab\rangle$, described by wave function $\Psi(a,b)$. Density matrices are written as ...
0
votes
0answers
26 views

What is the meaning of conformal mass on a branched manifold?

Consider the following QFT on the "branched" manifold, $\mathbb{H}^2 \times S^1_q$ where $S^1_q$ is an unit radius circle whose angular coordinate goes from $0$ to $2\pi q$, and hence the "branching". ...
1
vote
0answers
26 views

Standard references in (holographic) entanglement entropy literature (Part 2)

This is a continuation of this previously unanswered question, Standard references in (holographic) entanglement entropy literature (Part 1) I am wondering as to what are the standard references that ...
3
votes
3answers
106 views

Can I tell from one particle of an entangled pair whether the other particle has been observed?

I want to ask about a pair of entangled particles, each one heading towards a different group of experimenters. When one group observes their particle, is it possible for them to tell whether the ...
0
votes
1answer
64 views

Discrimination of Bell states on unkown qubits

Consider the scenario where Alice is given three qubits, and promised two of them are maximally entangled Bell state $\in_R \{\frac{|00+11>}{\sqrt{2}}, \frac{|00-11>}{\sqrt{2}}\}$ and one of ...
-1
votes
1answer
46 views

Does quantum teleportation lead to a change of quantum states?

Particles A and B are entangled, quantum information of particle A is transmitted to particle B via quantum teleportation, does particle B's quantum state change? What happens to particle A's quantum ...
1
vote
1answer
117 views

Question on the logic behind quantum computing

According to Wikipedia, "Quantum computing studies theoretical computation systems (quantum computers) that make direct use of quantum-mechanical phenomena, such as superposition and entanglement, to ...
1
vote
3answers
101 views

No-go theorems: when can we go there?

For a field founded on probability and uncertainty, QM seems to have quite a few "rules" describing what is not possible. Are there any circumstances under which the no communication, no cloning or ...
0
votes
2answers
42 views

Why are Alice's states in teleportation superpositions, not “pure” tensor states?

I'm trying to understand the Wikipedia article on quantum teleportation. Since the two particles of Alice are not entangled, all base states $|i\rangle\otimes|j\rangle$ for $i,j\in\{0, 1\}$ of the ...
-2
votes
2answers
70 views

In quantum mechanics does the truth/accuracy of a measurement really matter?

Once John Wheeler said "the past has no meaning or existence unless it exist as a record in the present". So, in a experiment of delayed choice entanglement swapping, if we used a faulty detector to ...
9
votes
3answers
429 views

Entanglement and coherence

I have come across a wonderful review of entanglement by Chris Drost in his answer to this post. One part that left me puzzled was: (This post is merely an attempt to understand a portion of Chris' ...
-1
votes
1answer
50 views

Can quantum entanglement work like this?

Lets say you have two entangled particles (A,B) and you already measured theirs spins and know that A has z+ and B has z- What will happen if after the measurement you will set the spin of B to z+ ...
1
vote
1answer
53 views

Question about what a simultaneous measurement of entangled spins means

I was working through a problem I found online and ran into something that is confusing me. We have a system of three spin-1/2 particles, in the state $$ |\psi\rangle = ...
0
votes
4answers
1k views

“FTL” Communication with Quantum Entanglement? [duplicate]

Can quantum entanglement make sending a message, whether audio, video, or even Morse code, instantaneous between two points (faster than it could travel normally at the speed of light)? Let me first ...
1
vote
0answers
37 views

What is special about quantum entanglement? [duplicate]

Get two pieces of paper. In secret write the same number on both papers. Transfer one paper to the Moon. Look to the paper which is left at the Earth. Voila! We know what is on the Moon paper. The ...
0
votes
2answers
49 views

Quantum entanglement thought experiment

One can "filter" a collection of electron pairs generated in an entangled (fixed-direction) spin state (e.g. singlet $\left|\uparrow \downarrow \right\rangle - \left|\downarrow \uparrow\right\rangle$) ...
0
votes
1answer
48 views

How to produce a given entangled state of two quantum bits?

I was watching Leonard Susskind's video series on quantum entanglement, where he looks at the spins of two electrons. In particular, there are entangled states of the form $$\alpha\left|\uparrow ...
0
votes
2answers
54 views

Pair Production in Entangled Photons

Two high-energy photons are entangled and go their separate ways. One of them undergoes pair production by interacting with an atomic nucleus, and this is observed. Does the other photon also undergo ...
3
votes
0answers
58 views

Standard references in (holographic) entanglement entropy literature (Part 1)

While writing a paper, I am wondering as to what are the standard references that one refers to for these various facts about entanglement entropy. I want to know as to what are the papers one should ...
0
votes
0answers
22 views

Construct bivariate symmetric (polynomial) Hilbert-Schmidt two-qubit volume functions over the unit square with certain properties

Construct bivariate symmetric polynomials (two-qubit volume functions) f(r,R) = f(R,r) >= 0 over [0,1]^2, with f(1,R) = f(r,1)=0, such that the univariate marginal (integrating over r or R) ...
2
votes
2answers
89 views

How can we know that all of the results for entangled photons are not chosen when the pair is created? [duplicate]

I was reading this introduction to quantum computing that says that when one photon in a pair of entangled photon is measured, the other one will have the opposite result when measured in the same ...
0
votes
1answer
338 views

How to understand locality and non-locality in Quantum Mechanics?

What actually is the definition of locality and non-locality? Does non-locality in Quantum Mechanics mean however far you separate 2 entangled atoms in space, the 2 atoms can still influence each ...
0
votes
1answer
50 views

How is entanglement possible? [duplicate]

If one particle is dependent on the other how can an action on one particle affect the state of another if when you measure a particle, the result you see is based off of something that technically ...
-1
votes
2answers
248 views

Faster-Than-Light Communication using Entangled Photons

Based on my understanding of the “Double-Slit Quantum Eraser Experiment”, documented here: http://grad.physics.sunysb.edu/~amarch/, it seems that Faster-Than-Light communication is possible. Of ...
1
vote
2answers
181 views

Do Entangled Particles communicate through Wormholes? [closed]

If so, would this “spooky action at a distance” still be spooky if that “distance” is actually shorter than it appears? Sorry if this is a Noob question. Just trying to understand how Entangled ...
-3
votes
2answers
143 views

Quantum Entanglement - How To Interpret [duplicate]

I have thought about quantum entanglement for some time, and I still don't quite understand the reasoning behind the conclusion that entangled particles somehow can communicate their state to each ...
0
votes
2answers
51 views

Does entanglement have to be verified synchronously

I am not a physicist so, first of all I like to apologise if I my question is stupid. I just want to know where I am going wrong here. But if I have understood anything about the entanglement ...
0
votes
1answer
51 views

Producing energy with entanglement

If we entangle two electrons for example and move one of the electron to Mars for instance. Are we able to somehow transfer the kinetic force of Mars from its movement (spinning and orbitting) to ...