PauliExpectation
class PauliExpectation(group_paulis=True)
Bases: qiskit.opflow.expectations.expectation_base.ExpectationBase
An Expectation converter for Pauli-basis observables by changing Pauli measurements to a diagonal ({Z, I}^n) basis and appending circuit post-rotations to the measured state function. Optionally groups the Paulis with the same post-rotations (those that commute with one another, or form Abelian groups) into single measurements to reduce circuit execution overhead.
Parameters
group_paulis (bool) – Whether to group the Pauli measurements into commuting sums, which all have the same diagonalizing circuit.
Methods Defined Here
compute_variance
PauliExpectation.compute_variance(exp_op)
Compute the variance of the expectation estimator.
Parameters
exp_op (OperatorBase) – The full expectation value Operator after sampling.
Return type
Union[list, float, ndarray]
Returns
The variances or lists thereof (if exp_op contains ListOps) of the expectation value estimation.
convert
PauliExpectation.convert(operator)
Accepts an Operator and returns a new Operator with the Pauli measurements replaced by diagonal Pauli post-rotation based measurements so they can be evaluated by sampling and averaging.
Parameters
operator (OperatorBase) – The operator to convert.
Return type
OperatorBase
Returns
The converted operator.