qiskit.opflow.expectations.MatrixExpectation¶
-
class
MatrixExpectation[source]¶ An Expectation converter which converts Operator measurements to be matrix-based so they can be evaluated by matrix multiplication.
-
__init__()¶ Initialize self. See help(type(self)) for accurate signature.
Methods
__init__()Initialize self.
compute_variance(exp_op)Compute the variance of the expectation estimator.
convert(operator)Accept an Operator and return a new Operator with the Pauli measurements replaced by Matrix based measurements.
-
compute_variance(exp_op)[source]¶ 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.- Return type
Union[list,float]- Returns
The variances or lists thereof (if exp_op contains ListOps) of the expectation value estimation, equal to 0.
-