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# SummedOp

`SummedOp(oplist, coeff=1.0, abelian=False)`GitHub(opens in a new tab)

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

Parameters

• oplist (`List`[`OperatorBase`]) – The Operators being summed.
• 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

`SummedOp.add(other)`GitHub(opens in a new tab)

Return Operator addition of `self` and `other`, overloaded by `+`.

Note

This appends `other` to `self.oplist` without checking `other` is already included or not. If you want to simplify them, please use `simplify()`.

Parameters

other (`OperatorBase`) – An `OperatorBase` with the same number of qubits as self, and in the same ‘Operator’, ‘State function’, or ‘Measurement’ category as self (i.e. the same type of underlying function).

Return type

`SummedOp`

Returns

A `SummedOp` equivalent to the sum of self and other.

### collapse_summands

`SummedOp.collapse_summands()`GitHub(opens in a new tab)

Return Operator by simplifying duplicate operators.

E.g., `SummedOp([2 * X ^ Y, X ^ Y]).collapse_summands() -> SummedOp([3 * X ^ Y])`.

Return type

`SummedOp`

Returns

A simplified `SummedOp` equivalent to self.

### equals

`SummedOp.equals(other)`GitHub(opens in a new tab)

Check if other is equal to self.

Note

This is not a mathematical check for equality. If `self` and `other` implement the same operation but differ in the representation (e.g. different type of summands) `equals` will evaluate to `False`.

Parameters

other (`OperatorBase`) – The other operator to check for equality.

Return type

`bool`

Returns

True, if other and self are equal, otherwise False.

Examples

``````>>> from qiskit.opflow import X, Z
>>> 2 * X == X + X
True
>>> X + Z == Z + X
True``````

### reduce

`SummedOp.reduce()`GitHub(opens in a new tab)

Try collapsing list or trees of sums.

Tries to sum up duplicate operators and reduces the operators in the sum.

Return type

`OperatorBase`

Returns

A collapsed version of self, if possible.

### to_circuit

`SummedOp.to_circuit()`GitHub(opens in a new tab)

Returns the quantum circuit, representing the SummedOp. In the first step, the SummedOp is converted to MatrixOp. This is straightforward for most operators, but it is not supported for operators containing parameterized PrimitiveOps (in that case, OpflowError is raised). In the next step, the MatrixOp representation of SummedOp is converted to circuit. In most cases, if the summands themselves are unitary operators, the SummedOp itself is non-unitary and can not be converted to circuit. In that case, ExtensionError is raised in the underlying modules.

Return type

`QuantumCircuit`

Returns

The circuit representation of the summed operator.

Raises

• OpflowError – if SummedOp can not be converted to MatrixOp (e.g. SummedOp is composed of
• parameterized PrimitiveOps**)****.** –

### to_matrix_op

`SummedOp.to_matrix_op(massive=False)`GitHub(opens in a new tab)

Returns an equivalent Operator composed of only NumPy-based primitives, such as `MatrixOp` and `VectorStateFn`.

Return type

`SummedOp`

### to_pauli_op

`SummedOp.to_pauli_op(massive=False)`GitHub(opens in a new tab)

Returns an equivalent Operator composed of only Pauli-based primitives, such as `PauliOp`.

Return type

`SummedOp`

## Attributes

`= '  '`

### 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`

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

Return settings.

Return type

`Dict`