Tagged Questions
6
votes
2answers
62 views
Is particle entanglement a binary property?
Is the particle entanglement a boolean property? That is, when we consider two given particles, is the answer to the question "are they entangled" always either "yes" or "no" (or, of course, "we are ...
1
vote
1answer
51 views
Can a link between photons that don't exist at the same time provide communication with the past?
They have published something about a link between photons that don't exist at the same time. Does this means that it is possible to build a device that will receive messages from itself but these ...
1
vote
1answer
41 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 ...
-1
votes
0answers
61 views
Quantum entanglement and speed of light $c$
On the topic of quantum entanglement, Wikipedia states:
Repeated experiments have verified that this works even when the measurements are performed more quickly than light could travel between the ...
1
vote
1answer
32 views
Name of a state with $d-1$ excitations, distributed uniformly among $n$ qudits
Is there a particular name for a quantum state of the form (up to the normalization):
$$\sum_{i_1+\ldots+i_n = d-1} |i_1\rangle |i_2\rangle \ldots |i_n\rangle$$
or was it studied is some papers?
...
6
votes
1answer
177 views
Entangled or unentangled?
I got a little puzzled when thinking about two entangled fermions.
Say that we have a Hilbert space in which we have two fermionic orbitals $a$ and $b$. Then the Hilbert space $H$'s dimension is just ...
1
vote
2answers
98 views
Is it only the spin of a particle that can be entangled with another particles spin?
Is it only the spin of a particle that can be entangled with another particles spin?
Also is there any good physical interpretation of the spin of a particle? because the rotational invariance of ...
5
votes
3answers
400 views
Does entanglement not immediately contradict the theory of special relativity?
Does entanglement not immediately contradict the theory of special relativity? Why are people still so convinced nothing can travel faster than light when we are perfectly aware of something that ...
3
votes
1answer
82 views
Questions about entanglement from a laymen/quantum hobbyist
Please note I am not a physicist I just read every article I can on it, I understand a good amount on it though. But no maths. (currently trying to learn the maths)
By what means can we as humans ...
1
vote
0answers
31 views
Trotter splitting and entanglement entropy
I have heard that a numerical solution to the Schrodinger equation using the Trotter splitting formula for a many-body Hamiltonian can cause an artificial increase in the entanglement entropy. I was ...
6
votes
4answers
252 views
Interference and which-path information
My understanding is that in a double-slit experiment, quantum interference disappears if which-path information is available. How is available defined? Consider the following experiment:
SPDC is used ...
2
votes
2answers
85 views
Von Neumann Entropy: varying definitions
I have seen different authors define von Neumann entropy in different ways. In particular, some use the natural logarithm and others log to base 2. What is the reasoning for this? Does it make any ...
1
vote
2answers
67 views
Schmidt basis: Entanglement
I do not understand how any state in Hilbert Space $\mathcal{H}=\mathcal{H}_A\otimes\mathcal{H}_B$ of dimension $\text{dim}(\mathcal{H}_A)\times\text{dim}(\mathcal{H}_B)$ can be decomposed in the ...
2
votes
4answers
131 views
Application of non maximally entangled state
In quantum information and quantum computation, we generally use Bell type states which are maximally entangled. I find that the set of entangled states as interesting objects from a mathematical ...
0
votes
1answer
101 views
Does the possibility of large scale entanglement mean 2-Body Problems are also unsolvable?
Experiments are showing that larger and larger objects can be entangled whereby proving that this quantum feature has no upper limit. Assuming this is true, does entangled celestial bodies mean even ...
1
vote
1answer
134 views
Coherence, Entanglement, Correlation
Let's deal specifically with a two-level system. I understand that ``coherence'' is due to the off-diagonal elements in the density matrix $\rho(t) = \sum_{i}|\psi_i(t)\rangle p_i\langle\psi_i(t)|$ ...
0
votes
0answers
74 views
Impulse travelling faster than light
There have been conducted many experiments in which light impulses traveled faster than light like the one in Princeton in 2000. This phenomenon has something to do with quantum entanglement. Does ...
5
votes
0answers
114 views
Local explanation of the Aharonov-Bohm effect in terms of force fields
Here is an interesting paper for the Physics SE community: On the role of potentials in the Aharonov-Bohm effect, Lev Vaidman, published in PHYSICAL REVIEW A 86, 040101(R) (2012).
You should check it ...
3
votes
1answer
63 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 ...
2
votes
2answers
124 views
What properties are entangled in quantum entanglement?
When two particles are entangled, one can measure the properties of one of the particles and instantaneously know the properties of the other. This is because the two particles possess the same ...
2
votes
2answers
171 views
Does the reduced density matrix describes a real mixed state?
Suppose that we have two entangled particles A and B with pure state vector
$|\psi\rangle=a|0\rangle_A |1\rangle_B + b|1\rangle_A |0\rangle_B \hspace{1cm}(1)$
When we take the partial trace over the ...
1
vote
2answers
143 views
Understanding on quantum entanglement
Understanding on quantum entanglement? I am very vague on this topic and would appreciate a detailed explanation on this phenomenon.
Also what are the possible applied uses for quantum entanglement? ...
0
votes
1answer
107 views
Creating entanglement by measuring in a certain basis
This is one of the problems from Assignment 2 from CS191x at edx.org, so please do not post explicit answers.
We have two qubits in the state |0+⟩ and we want to entangle them by
performing a ...
-1
votes
1answer
308 views
EPR-type experiments and faster-than-light communication using interference effects as signaling mechanism
I understand that faster-than-light communication is impossible when making single measurements, because the outcome of each measurement is random. However, shouldn't measurement on one side collapse ...
0
votes
1answer
97 views
Particles entangled after the big bang
Is that true that the big bang caused the quantum entanglement of all the particles of the universe so every particle is entangled to each other particle of the universe?
28
votes
7answers
2k 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
1answer
147 views
Quantum Mechanics proved incorrect. Bohr - Einstein debates concluded?
"Photons act like they go through two paths, even when we know which they took".
Please refer the above link and its conclusion.
I am an Engineer. What I infer from this is :-
This proves ERP.
...
3
votes
1answer
96 views
three-particle quantum entanglement
So I know that two particles can be entangled in a quantum way, but is it possible that more than two particles be entangled in a quantum way? Most descriptions provide with two-particles cases, so I ...
3
votes
0answers
150 views
Quantum Entanglement Versus Inflation in the Early Universe?
Quantum entanglement is one of the most fascinating and mysterious phenomena in nature. It needs no interactions, or any sort of exchange for it to take place. It is possible, not against any rules of ...
1
vote
1answer
91 views
Data For Quantum Entanglement
Is there any publicly accessible data that shows quantum entanglement empirically.
I want to see what these researches are seeing that is showing them that indeed this phenomenon is real.
Also, any ...
2
votes
2answers
315 views
When and how did the idea of the tensor product originate in the history quantum mechanics?
At some point in the history of quantum mechanics, it was accepted that a single particle is described by a wavefunction which is a function of the position of the particle $\mathbf{r}$, denoted:
...
12
votes
1answer
214 views
Can path integrals be used to understand entanglement?
I like path integrals. I prefer to try to understand quantum phenomena in terms of path integrals rather than Hamiltonian mechanics. However, most of the standard texts on quantum mechanics start from ...
6
votes
1answer
191 views
Why do we want to entangle qubits?
The title is pretty much all I want to ask. Why are qubits entangled? To my knowledge (which isn't that deep) a quantum register can be realized without entangling the qubits.
3
votes
1answer
171 views
System with no entanglement but consuming quantum discord
I have come across an article which talks about quantum discord (Observing the operational significance of discord consumption. M. Gu et al. Nature Physics 8, 671–675 (2012) doi:10.1038/nphys2376), ...
2
votes
2answers
167 views
Can we determine whether or not a particle is entangled?
Suppose Shaniqua and Tyrone have four pairs, a, b, c, and d, of entangled particles. They take their particles and go very far apart. If Tyrone can determine whether or not a particle is still ...
-1
votes
2answers
121 views
Which book describe all experiments related to quantum mechanic especially entanglement and photon? [closed]
Which book describe all experiments related to quantum mechanic especially entanglement and photon?
I expect this book to describe where to buy detector and thing to create entanglement, or how to ...
2
votes
0answers
57 views
How to make timelike entanglement in the laboratory?
http://io9.com/5744143/particles-can-be-quantum-entangled-through-time-as-well-as-space
http://arxiv.org/abs/1101.2565
How to make timelike entanglement in the laboratory?
How to test whether mixed ...
4
votes
4answers
556 views
Entangled electron-positron pair
Usually when we talk about entanglement, we mean entangled spin states (of electrons) or polarizations (of photons). My questions are:
Does pair production guarantee the product electron and ...
2
votes
4answers
199 views
Does measuring destroy entanglement
Before measuring a quantum particle(photon) it exists in a superposition state, once we observe(measure) it, it settles in one of the possible states(destroying superposition).
For entangled ...
0
votes
1answer
90 views
Would synchronized dancing be a good way to describe entangled atoms to a laymen?
I was talking my professor about entanglement swapping between light and matter and it is briefly described here:
You start out with a crystal capable of doing parametric down conversion of incoming ...
-1
votes
3answers
283 views
Using quantum entanglement to send messages back to the past [duplicate]
Possible Duplicate:
Entanglement in time
I heard that there is an experiment that uses quantum entanglement to try to send messages back to the past. I am having a hard time understanding ...
5
votes
1answer
329 views
Topological Order and Entanglement
I have a question about entanglement in condensed matter physics. It seems that topological order origins from long range entanglement, but what is long range entanglement? It is the same as long ...
2
votes
2answers
314 views
What is the difference between Quantum teleportation and Radio waves?
Quantum teleportation over 143 kilometres using active feed- forward
What is the difference between Quantum teleportation and radio waves?
0
votes
0answers
103 views
Can experiment distinguish the basis in which a singlet state is represented?
Let $\left(|\uparrow\rangle,|\downarrow\rangle\right)$ and $\left(|\nearrow\rangle,|\swarrow\rangle\right)$ be two bases of the $2$-dimensional Hilbert space $H$.
Can an experiment distinguish ...
3
votes
1answer
221 views
Defining entanglement in subspaces of tensor product
I have asked the question in math.stackexchange, but perhaps it should be more relevant here. Hence I am re-posting it with necessary reediting.
Let $\mathcal{H}=\mathbb{C}^n$ be a Hilbert space. A ...
3
votes
0answers
138 views
Spin polarization of decay products
A relativistic moving particle, e.g. muon $\mu^+$, described by its four-momentum vector $p_\mu$, charge $e$ and with a given spin polarization, ${\bf S}=(S_x,S_y,S_z)$, decays into three particles, ...
1
vote
2answers
108 views
Can double entanglement preserve correlations?
We have 2 EPR experiments running in parallel, with Alice having one leg of each (a1,a2) and Bob the other leg of each (b1,b2). Thus (a1,b1) are anticorrelated, as are (a2,b2). Thus also (a1,a2) are ...
4
votes
1answer
145 views
Can entanglement swapping be performed on already-entangled photons, and if so, can it preserve this entanglement over the swap?
Consider 2 uncorrelated photon pairs (a1,a2), (b1,b2) such that (a1,a2) are entangled, and separately (b1,b2) are entangled. We wish to entangle-swap so as to end up with a new entanglement (a1,b1) by ...
3
votes
0answers
52 views
Why do we think that quantum entanglement implies action at a distance? [duplicate]
Possible Duplicate:
Why quantum entanglement is considered to be active link between particles?
I am a layman trying to read into quantum mechanics. As I understand it quantum entanglement ...
2
votes
1answer
135 views
What does the notation $|x_1,x_2\rangle$ mean?
I would like clarification on an equation in the paper "Free matter wave packet teleportation via cold-molecule dynamics", L. Fisch and G. Kurizki, Europhysics Letters 75 (2006), pp. 847-853, DOI: ...
