Questions tagged [concurrence]
A quantification of quantum entanglement that also serves as a separability criterion. Concurrence equal to zero indicates an unentangled/separable state. A non-zero concurrence "quantifies" how far the states in question are from achieving separability.
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How to get to the formula for the entanglement of formation of two-qubit states?
An explicit formula for the entanglement of formation $E(\rho)$ for an arbitrary two-qubit state $\rho$ was given by Wooters in Entanglement of Formation of an Arbitrary State of Two Qubits. The ...
glS♦
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Why does $\sigma_y$ seem to have a special role in the two-qubit concurrence?
The concurrence of a two-qubit state $\rho$ can be written as
$$\mathcal C(\rho) = \max(0, \lambda_1-\lambda_2-\lambda_3-\lambda_4),$$
where $\lambda_i$ are the eigenvalues of $|\sqrt\rho\sqrt{\tilde\...
glS♦
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Why do we use complex-conjugate instead of complex-conjugate-transpose when calculating the concurrence?
When we use the formula to calculate two-qubit entanglement, like these:
$$
C(\rho)=\max \left\{\sqrt{e_{1}}-\sqrt{e_{2}}-\sqrt{e_{3}}-\sqrt{e_{4}}, 0\right\}\tag{18}
$$
with the quantities $...
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Connection between the definitions of concurrence for a two-qubit states
The concurrence for a state $\rho$ as defined here is
\begin{equation}
C(\rho) = {\rm max}\{0, \lambda_1-\lambda_2-\lambda_3-\lambda_4\}.
\end{equation}
Where $\lambda_i$ are the eigenvalues of matrix ...
glS♦
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What is the relation between fidelity and concurrence for a two qubit maximally mixed state?
I am trying to understand the relation between Fidelity and Concurrence for a two qubit maximally mixed state. When I calculate the Fidelity and Concurrence, I observe that Concurrence is zero whereas ...
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How to sample from the uniform distribution over the tensor product of two Bloch spheres?
For some context, I am trying to assess the capacity that certain two qubit gates have to create entanglement. To do this I am using the idea of "entangling power", where one takes their ...
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Can two states with the same entanglement be transformed into each other using local unitaries?
Take two pure bi-partite states $\psi$ and $\phi$ that have the same amount of entanglement in them as quantified by concurrence (does the measure make a difference?). Can any such states be ...
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