Concurrence as a measure of entanglement

  • #1

Main Question or Discussion Point

In book Quantum computing explained by David Mahon concurrence, as a measure of entanglement is defined as
[tex]C(\psi)=|\langle \psi|\tilde{\psi} \rangle |[/tex]
where ##|\psi\rangle=Y \otimes Y|\psi^*\rangle##
or with density matrix
##\rho(Y \otimes Y)\rho^{\dagger}(Y \otimes Y)##.
Could someone explain me what is ##|\tilde{\psi}\rangle## and ##Y##?
 

Answers and Replies

  • #2
DrClaude
Mentor
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where ##|\psi\rangle=Y \otimes Y|\psi^*\rangle##
or with density matrix
##\rho(Y \otimes Y)\rho^{\dagger}(Y \otimes Y)##.
That's actually
$$|\tilde{\psi} \rangle=Y \otimes Y|\psi^*\rangle $$
and
$$
\tilde{\rho} = (Y \otimes Y)\rho^{\dagger}(Y \otimes Y)
$$
##Y## is the Pauli spin matrix ##\sigma_y##.
 

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