# ComposedOp¶

class ComposedOp(oplist, coeff=1.0, abelian=False)[source]

Bases: qiskit.opflow.list_ops.list_op.ListOp

A class for lazily representing compositions of Operators. Often Operators cannot be efficiently composed with one another, but may be manipulated further so that they can be composed later. This class holds logic to indicate that the Operators in oplist are meant to be composed, and therefore if they reach a point in which they can be, such as after conversion to QuantumCircuits or matrices, they can be reduced by composition.

Parameters
• oplist (List[OperatorBase]) – The Operators being composed.

• coeff (Union[complex, ParameterExpression]) – A coefficient multiplying the operator

• abelian (bool) – Indicates whether the Operators in oplist are known to mutually commute.

Methods Defined Here

 adjoint Return a new Operator equal to the Operator’s adjoint (conjugate transpose), overloaded by ~. compose Return Operator Composition between self and other (linear algebra-style: A@B(x) = A(B(x))), overloaded by @. eval Evaluate the Operator’s underlying function, either on a binary string or another Operator. non_distributive_reduce Reduce without attempting to expand all distributive compositions. reduce Try collapsing the Operator structure, usually after some type of conversion, e.g. to_circuit Returns the quantum circuit, representing the composed operator.

Attributes

INDENTATION = ' '
abelian

Whether the Operators in oplist are known to commute with one another.

Return type

bool

Returns

A bool indicating whether the oplist is Abelian.

coeff

The scalar coefficient multiplying the Operator.

Return type

Union[complex, ParameterExpression]

Returns

The coefficient.

combo_fn

The function defining how to combine oplist (or Numbers, or NumPy arrays) to produce the Operator’s underlying function. For example, SummedOp’s combination function is to add all of the Operators in oplist.

Return type

Callable

Returns

The combination function.

distributive
Return type

bool

grad_combo_fn

The gradient of combo_fn.

Return type

Optional[Callable]

instance_id

Return the unique instance id.

Return type

int

num_qubits
Return type

int

oplist

The list of OperatorBases defining the underlying function of this Operator.

Return type

List[OperatorBase]

Returns

The Operators defining the ListOp

parameters
settings

Return settings.

Return type

Dict