# cirq.qis.operation_to_choi

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.

[{ "type": "thumb-down", "id": "missingTheInformationINeed", "label":"Missing the information I need" },{ "type": "thumb-down", "id": "tooComplicatedTooManySteps", "label":"Too complicated / too many steps" },{ "type": "thumb-down", "id": "outOfDate", "label":"Out of date" },{ "type": "thumb-down", "id": "samplesCodeIssue", "label":"Samples / code issue" },{ "type": "thumb-down", "id": "otherDown", "label":"Other" }]
[{ "type": "thumb-up", "id": "easyToUnderstand", "label":"Easy to understand" },{ "type": "thumb-up", "id": "solvedMyProblem", "label":"Solved my problem" },{ "type": "thumb-up", "id": "otherUp", "label":"Other" }]