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Returns entanglement fidelity of a given quantum channel.

Entanglement fidelity \(F_e\) of a quantum channel \(E: L(H) \to L(H)\) is the overlap between the maximally entangled state \(|\phi\rangle = \frac{1}{\sqrt{dim H} } \sum_i|i\rangle|i\rangle\) and the state obtained by sending one half of \(|\phi\rangle\) through the channel \(E\), i.e.

F_e = \langle\phi|(E \otimes I)(|\phi\rangle\langle\phi|)|\phi\rangle

where \(I: L(H) \to L(H)\) is the identity map.

operation Quantum channel whose entanglement fidelity is to be computed.

Entanglement fidelity of the channel represented by operation.