# SummedOp

*class *`qiskit.opflow.list_ops.SummedOp(oplist, coeff=1.0, abelian=False)`

Bases: `ListOp`

Deprecated: 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.

The class `qiskit.opflow.list_ops.summed_op.SummedOp`

is deprecated as of qiskit-terra 0.24.0. It will be removed no earlier than 3 months after the release date. For code migration guidelines, visit https://qisk.it/opflow_migration.

**Parameters**

**oplist**(*List**[**OperatorBase**]*) – The Operators being summed.**coeff**(*complex**|**ParameterExpression*) – A coefficient multiplying the operator**abelian**(*bool*) – Indicates whether the Operators in`oplist`

are known to mutually commute.

## Attributes

### INDENTATION

Default value: `' '`

### abelian

Whether the Operators in `oplist`

are known to commute with one another.

**Returns**

A bool indicating whether the `oplist`

is Abelian.

### coeff

The scalar coefficient multiplying the Operator.

**Returns**

The coefficient.

### coeffs

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

### 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`

.

**Returns**

The combination function.

### distributive

### grad_combo_fn

The gradient of `combo_fn`

.

### instance_id

Return the unique instance id.

### num_qubits

### oplist

The list of `OperatorBases`

defining the underlying function of this Operator.

**Returns**

The Operators defining the ListOp

### parameters

### settings

Return settings.

## Methods

### add

`add(other)`

Return Operator addition of `self`

and `other`

, overloaded by `+`

.

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).

**Returns**

A `SummedOp`

equivalent to the sum of self and other.

**Return type**

### collapse_summands

`collapse_summands()`

Return Operator by simplifying duplicate operators.

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

.

**Returns**

A simplified `SummedOp`

equivalent to self.

**Return type**

### equals

`equals(other)`

Check if other is equal to self.

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.

**Returns**

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

**Return type**

**Examples**

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

### reduce

`reduce()`

Try collapsing list or trees of sums.

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

**Returns**

A collapsed version of self, if possible.

**Return type**

### to_circuit

`to_circuit()`

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.

**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****)****.** –

**Return type**

### to_matrix_op

`to_matrix_op(massive=False)`

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

and `VectorStateFn`

.

**Return type**

### to_pauli_op

`to_pauli_op(massive=False)`

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

.

**Return type**