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Newest 'entanglement' Questions - Quantum Computing Stack Exchange
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Learn more about TeamsQuestions tagged [entanglement]
For questions about the principle and application of quantum entanglement. It is a physical phenomenon which occurs when pairs or groups of particles are generated, interact, or share spatial proximity in ways such that the quantum state of each particle cannot be described independently of the state of the other(s), even when the particles are separated by a large distance—instead, a quantum state must be described for the system as a whole. (Wikipedia)
913 questions
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3
votes
1
answer
162
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Understanding Mermin-Peres magic square game
I am new in quantum information, and I am trying to understand the quantum winning strategy for winning in the Mermin-Peres magic square game. The game has different versions, I am looking at the ...
0
votes
0
answers
79
views
How do you perform technically quantum teleportation?
Here is below the well-known quantum teleportation protocol, which can be viewed as the quantum version of the classical one-time pad.
Indeed, in the classical one-time pad, the same bit $s$ is sent ...
1
vote
2
answers
158
views
Quantum Teleportation and Quantum Internet
As far as I understand, Quantum Internet is the idea of exchanging quantum bits, and then quantum states, just like current internet exchanges classical bits. The interest is that it would allow to ...
4
votes
1
answer
174
views
Are there fundamental differences between the four different Bell states?
I was thinking about the potential differences between the four Bell states:
$|\Phi^{\pm}\rangle = \frac{1}{\sqrt{2}} \left( |00\rangle \pm |11\rangle\right)$
$|\Psi^{\pm}\rangle = \frac{1}{\sqrt{2}} \...
1
vote
0
answers
34
views
Is there an entanglement metric that satisfies metric space axioms, like the variation of information?
Given a bipartition of a quantum system into subsystems $A$ and $B$, one can construct reduced density matrices
$$ \rho^{A} = \operatorname{Tr}_{B}[\rho^{AB}], $$
for state $\rho^{AB}$ on the whole ...
0
votes
0
answers
18
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What is the annealed average and quenched average of random quantum circuits
I wonder how to distinguish between the annealed and quenched averages in random quantum circuits. Is the former a characterization of the average state, and the latter the average characterization ...
2
votes
1
answer
166
views
The entanglement of the subsystem of n-qubits Haar random states
For n-qubits Haar random states, what is the max theoretical expectation value of the Von Neumann entropy obtained by cutting the system?
1
vote
1
answer
81
views
why the concurrence depends on phases?
I'm studying entanglement in pure two-qubit states and came across a situation where the state is written with complex phases as:
$
|\psi\rangle = \alpha e^{i f_1} |00\rangle + \beta e^{i f_2} |01\...
- 847
1
vote
1
answer
56
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How to reset ancilla after swapping when original ancilla flipping condition is not available?
Following little-endian format, I have the following state, which is part of a larger superposition of 6 qubits:
$$
\alpha|0\rangle_{swap\_ancilla}|010010\rangle + \beta|0\rangle_{swap\_ancilla}|...
2
votes
1
answer
129
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Does copying quantum registers using CNOT onto auxillary registers affect final outcome?
Say I have a series of unitary $U_1, U_2, \ldots, U_t$ that acts on register $x,y$ (each with n-qubits). Now say I introduce auxillary registers $z_1, z_2$ initalized to be zero and let $\mathsf{CNOT}...
2
votes
1
answer
165
views
Compact error detection cirquit for five-qubit perfect code
I am currently working on modelling distillation factories for remote entanglement. For five-qubit code my circuit is as follows:
Share 5 noisy bell states between processors (encoded into 5 surface ...
9
votes
1
answer
156
views
Which two-qubit Hamiltonians $H$ keep $e^{-iHt} |00\rangle$ a product state?
How can I classify all two-qubit Hamiltonians $H$ such that $e^{-iHt}|00\rangle$ is unentangled for all times $t?$
This question is warm-up for several related questions of mine: 816017, 797030, but I ...
2
votes
1
answer
87
views
Complexity of deciding whether a subcomponent of a pure state is unentangled
Suppose I have an $n$-qubit pure state $|\psi\rangle$ that I can prepare using a unitary $U$ s.t. $U|0\rangle = |\psi\rangle$. I would like to determine whether the first qubit in the system is ...
4
votes
2
answers
182
views
Maximum overlap between an entangled state and a product state
Say we have an entangled state $\left| \phi \right\rangle_{AB}$ and a product state $ \left| \psi \right\rangle_A \otimes \left| \psi \right\rangle_B$ , how can we show that their maximum overlap is ...
3
votes
2
answers
287
views
Question about Haar random states
Consider two independently sampled Haar random unitary $U$ and $V$, each of which acts on $n$ qubits.
Consider the state
\begin{equation}
|\psi\rangle = (U \otimes V) |0^{\otimes 2n}\rangle.
\end{...
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