# qiskit.opflow.expectations.MatrixExpectation.compute_variance¶

MatrixExpectation.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.