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# ComposedOp¶

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

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. `to_matrix` Return NumPy representation of the 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.

coeffs

Return a list of the coefficients of the operators listed. Raises exception for nested Listops.

Return type

`List`[`Union`[`complex`, `ParameterExpression`]]

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`

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`