Returns the unique Choi matrix associated with an operation .

Choi matrix J(E) of a linear map E: L(H1) -> L(H2) which takes linear operators on Hilbert space H1 to linear operators on Hilbert space H2 is defined as

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

where \(|\phi\rangle = \sum_i|i\rangle|i\rangle\) is the unnormalized maximally entangled state and I: L(H1) -> L(H1) is the identity map. Note that J(E) is a square matrix with d1*d2 rows and columns where d1 = dim H1 and d2 = dim H2.

operation Quantum channel.

Choi matrix corresponding to operation.