---
title: evolved_operator_ansatz (v1.3)
description: API reference for qiskit.circuit.library.evolved_operator_ansatz in qiskit v1.3
source: https://eu-de.quantum.cloud.ibm.com/docs/en/api/qiskit/1.3/qiskit.circuit.library.evolved_operator_ansatz
---

# evolved\_operator\_ansatz

*class* `qiskit.circuit.library.evolved_operator_ansatz(operators, reps=1, evolution=None, insert_barriers=False, name='EvolvedOps', parameter_prefix='t', remove_identities=True, flatten=None)`

[GitHub](https://github.com/Qiskit/qiskit/tree/stable/1.3/qiskit/circuit/library/n_local/evolved_operator_ansatz.py#L39-L184)

Bases:

Construct an ansatz out of operator evolutions.

For a set of operators $[O_1, ..., O_J]$ and $R$ repetitions (`reps`), this circuit is defined as

$$
\prod_{r=1}^{R} \left( \prod_{j=J}^1 e^{-i\theta_{j, r} O_j} \right)
$$

where the exponentials $exp(-i\theta O_j)$ are expanded using the product formula specified by `evolution`.

**Examples**

```python
from qiskit.circuit.library import evolved_operator_ansatz
from qiskit.quantum_info import Pauli

ops = [Pauli("ZZI"), Pauli("IZZ"), Pauli("IXI")]
ansatz = evolved_operator_ansatz(ops, reps=3, insert_barriers=True)
ansatz.draw("mpl")
```

![Circuit diagram output by the previous code.](https://eu-de.quantum.cloud.ibm.com/docs/images/api/qiskit/1.3/qiskit-circuit-library-evolved_operator_ansatz-1.avif)

**Parameters**

- **operators** (*BaseOperator | Sequence\[BaseOperator]*) – The operators to evolve. Can be a single operator or a sequence thereof.
- **reps** ([*int*](https://docs.python.org/3/library/functions.html#int)) – The number of times to repeat the evolved operators.
- **evolution** ([*EvolutionSynthesis*](/docs/api/qiskit/1.3/qiskit.synthesis.EvolutionSynthesis "qiskit.synthesis.EvolutionSynthesis") *| None*) – A specification of which evolution synthesis to use for the [`PauliEvolutionGate`](/docs/api/qiskit/1.3/qiskit.circuit.library.PauliEvolutionGate "qiskit.circuit.library.PauliEvolutionGate"). Defaults to first order Trotterization. Note, that operators of type [`Operator`](/docs/api/qiskit/1.3/qiskit.quantum_info.Operator "qiskit.quantum_info.Operator") are evolved using the [`HamiltonianGate`](/docs/api/qiskit/1.3/qiskit.circuit.library.HamiltonianGate "qiskit.circuit.library.HamiltonianGate"), as there are no Hamiltonian terms to expand in Trotterization.
- **insert\_barriers** ([*bool*](https://docs.python.org/3/library/functions.html#bool)) – Whether to insert barriers in between each evolution.
- **name** ([*str*](https://docs.python.org/3/library/stdtypes.html#str)) – The name of the circuit.
- **parameter\_prefix** ([*str*](https://docs.python.org/3/library/stdtypes.html#str) *| Sequence\[*[*str*](https://docs.python.org/3/library/stdtypes.html#str)*]*) – Set the names of the circuit parameters. If a string, the same prefix will be used for each parameters. Can also be a list to specify a prefix per operator.
- **remove\_identities** ([*bool*](https://docs.python.org/3/library/functions.html#bool)) – If `True`, ignore identity operators (note that we do not check [`Operator`](/docs/api/qiskit/1.3/qiskit.quantum_info.Operator "qiskit.quantum_info.Operator") inputs). This will also remove parameters associated with identities.
- **flatten** ([*bool*](https://docs.python.org/3/library/functions.html#bool) *| None*) – If `True`, a flat circuit is returned instead of nesting it inside multiple layers of gate objects. Setting this to `False` is significantly less performant, especially for parameter binding, but can be desirable for a cleaner visualization.

**Return type**

[QuantumCircuit](/docs/api/qiskit/1.3/qiskit.circuit.QuantumCircuit "qiskit.circuit.QuantumCircuit")