MatrixExpectation
class qiskit.opflow.expectations.MatrixExpectation
Bases: ExpectationBase
An Expectation converter which converts Operator measurements to be matrix-based so they can be evaluated by matrix multiplication.
The class qiskit.opflow.expectations.matrix_expectation.MatrixExpectation is deprecated as of qiskit-terra 0.24.0. It will be removed in the Qiskit 1.0 release. For code migration guidelines, visit https://qisk.it/opflow_migration(opens in a new tab).
Methods
compute_variance
compute_variance(exp_op)
Compute the variance of the expectation estimator. Because this expectation works by matrix multiplication, the estimation is exact and the variance is always 0, but we need to return those values in a way which matches the Operator’s structure.
Parameters
exp_op (OperatorBase) – The full expectation value Operator.
Returns
The variances or lists thereof (if exp_op contains ListOps) of the expectation value estimation, equal to 0.
Return type
convert
convert(operator)
Accept an Operator and return a new Operator with the Pauli measurements replaced by Matrix based measurements.
Parameters
operator (OperatorBase) – The operator to convert.
Returns
The converted operator.
Return type