All Questions
Tagged with quantum-entanglement hilbert-space
27
questions
23
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6
answers
6k
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How do we know that entanglement allows measurement to instantly change the other particle's state? [duplicate]
I have never found experimental evidence that measuring one entangled particle causes the state of the other entangled particle to change, rather than just being revealed.
Using the spin up spin down ...
- 247
9
votes
3
answers
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What is quantum entanglement? [closed]
What is quantum entanglement?
Please be pedagogical.
Edit: I have updated my background under my profile.
- 455
19
votes
1
answer
3k
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Is purification physically meaningful?
Consider a quantum system with Hilbert space $\mathscr{H}$ and suppose the quantum state is specified by a density operator $\rho$. Since it is Hermitian, it has a spectral decomposition: $$\rho = \...
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22
votes
3
answers
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What is a completely positive map *physically*?
This can be considered as a continuation of this question.
What does it mean to be a completely positive map, from a Physics point of view?
A positive map $h:\mathcal{B(H)}\rightarrow\mathcal{B(K)}$ ...
- 1,049
11
votes
3
answers
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What is the minimum number of separable pure states needed to decompose arbitrary separable states?
Consider a separable state $\rho$ living in a tensor product space $\mathcal H\otimes\mathcal H'$, with $\mathcal H$ and $\mathcal H'$ of dimensions $D$ and $D'$, respectively.
If $\rho$ is separable, ...
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9
votes
2
answers
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How are entangled states created?
I understand that when I have two separate states that their combination state increases the Hilbert Space to
$|\psi_1\rangle \otimes |\psi_2\rangle$
For example, looking at a simple example where ...
- 2,193
16
votes
5
answers
5k
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How do tensor products and direct sums fit into quantum mechanics?
I understand that at times tensor products or direct sums are taken between Hilbert spaces in quantum mechanics. I don't, however, know when this can be done or when it should be done. I would like ...
user113773
16
votes
3
answers
2k
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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 ...
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9
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1
answer
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Methods to distinguish between pure/mixed states and entangled/separable states
I'm a little confused about how we can distinguish between pure/mixed states and entangled/separable states and I would really appreciate some help!
I understand a density operator $\rho$ represents ...
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3
votes
1
answer
139
views
Is there a relation between some kind of distance and the Schmidt basis?
Consider two bipartite quantum states $|\phi\rangle^{AB}$ and $|\psi\rangle^{AB}$ (in a finite dimensional Hilbert space $\mathcal H_A\otimes \mathcal H_B$), such that
$$\| |\phi\rangle\langle\phi|^{...
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2
votes
4
answers
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Definition of Entanglement
The definition of quantum entanglement, found on the internet and the literature is:
On a bipartite system $\mathcal{H}_A \otimes \mathcal{H}_B$, let $\rho$ be a mixed state. It is said to be ...
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2
votes
2
answers
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$mn$-dim Hilbert space vs product of $m$ and $n$ Hilbert spaces
Assume one has a Hilbert space $\mathcal{H}_K$ of dimension $K=mn$. Associated to it, there exists a set of all possible quantum transformations $\mathcal{E}$. Of those, the most important are, of ...
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10
votes
2
answers
2k
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Does correlation of the measurement outcomes imply that a state is entangled?
As per Wikipedia:
Quantum entanglement is a physical phenomenon that occurs when pairs or groups of particles are generated or interact in ways such that the quantum state of each particle cannot ...
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8
votes
1
answer
3k
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Quantum circuit for a $3$-qubit $|W \rangle$ state [closed]
Can someone specify a quantum circuit that will deterministically output the $3$-qubit $|W \rangle$ state, if the input to the circuit is $|0,0,0 \rangle$? Or, is there a quantum circuit with a ...
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6
votes
2
answers
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What are the relations between mixed/pure and separable/entangled states?
I read this question which clarified the concepts of mixed/pure/separable/entangled states, but I can't see if one of "mixed/pure" implies one of "separable/entangled" and/or vice ...
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