---
title: PauliTwoDesign (v2.1)
description: API reference for qiskit.circuit.library.PauliTwoDesign in qiskit v2.1
source: https://eu-de.quantum.cloud.ibm.com/docs/en/api/qiskit/2.1/qiskit.circuit.library.PauliTwoDesign
---

# PauliTwoDesign

*class* `qiskit.circuit.library.PauliTwoDesign(num_qubits=None, reps=3, seed=None, insert_barriers=False, name='PauliTwoDesign')`

[GitHub](https://github.com/Qiskit/qiskit/tree/stable/2.1/qiskit/circuit/library/n_local/pauli_two_design.py#L121-L246)

Bases: [`TwoLocal`](/docs/api/qiskit/2.1/qiskit.circuit.library.TwoLocal "qiskit.circuit.library.n_local.two_local.TwoLocal")

The Pauli Two-Design ansatz.

This class implements a particular form of a 2-design circuit \[1], which is frequently studied in quantum machine learning literature, such as e.g. the investigating of Barren plateaus in variational algorithms \[2].

The circuit consists of alternating rotation and entanglement layers with an initial layer of $\sqrt{H} = RY(\pi/4)$ gates. The rotation layers contain single qubit Pauli rotations, where the axis is chosen uniformly at random to be X, Y or Z. The entanglement layers is compromised of pairwise CZ gates with a total depth of 2.

For instance, the circuit could look like this (but note that choosing a different seed yields different Pauli rotations).

```text
     ┌─────────┐┌──────────┐       ░ ┌──────────┐       ░  ┌──────────┐
q_0: ┤ RY(π/4) ├┤ RZ(θ[0]) ├─■─────░─┤ RY(θ[4]) ├─■─────░──┤ RZ(θ[8]) ├
     ├─────────┤├──────────┤ │     ░ ├──────────┤ │     ░  ├──────────┤
q_1: ┤ RY(π/4) ├┤ RZ(θ[1]) ├─■──■──░─┤ RY(θ[5]) ├─■──■──░──┤ RX(θ[9]) ├
     ├─────────┤├──────────┤    │  ░ ├──────────┤    │  ░ ┌┴──────────┤
q_2: ┤ RY(π/4) ├┤ RX(θ[2]) ├─■──■──░─┤ RY(θ[6]) ├─■──■──░─┤ RX(θ[10]) ├
     ├─────────┤├──────────┤ │     ░ ├──────────┤ │     ░ ├───────────┤
q_3: ┤ RY(π/4) ├┤ RZ(θ[3]) ├─■─────░─┤ RX(θ[7]) ├─■─────░─┤ RY(θ[11]) ├
     └─────────┘└──────────┘       ░ └──────────┘       ░ └───────────┘
```

**Examples**

```python
from qiskit.circuit.library import PauliTwoDesign
circuit = PauliTwoDesign(4, reps=2, seed=5, insert_barriers=True)
circuit.draw('mpl')
```

![Circuit diagram output by the previous code.](https://eu-de.quantum.cloud.ibm.com/docs/images/api/qiskit/2.1/qiskit-circuit-library-PauliTwoDesign-1.avif)

> **See also**
>
> The [`pauli_two_design()`](/docs/api/qiskit/2.1/qiskit.circuit.library.pauli_two_design "qiskit.circuit.library.pauli_two_design") function constructs the functionally same circuit, but faster.

**References**

**\[1]: Nakata et al., Unitary 2-designs from random X- and Z-diagonal unitaries.**

[arXiv:1502.07514](https://arxiv.org/pdf/1502.07514.pdf)

**\[2]: McClean et al., Barren plateaus in quantum neural network training landscapes.**

[arXiv:1803.11173](https://arxiv.org/pdf/1803.11173.pdf)

> **Deprecated since version 2.1**
>
> The class `qiskit.circuit.library.n_local.pauli_two_design.PauliTwoDesign` is deprecated as of Qiskit 2.1. It will be removed in Qiskit 3.0. Use the function qiskit.circuit.library.pauli\_two\_design instead.

**Parameters**

- **num\_qubits** ([*int*](https://docs.python.org/3/library/functions.html#int) *| None*) – The number of qubits of the Pauli Two-Design circuit.
- **reps** ([*int*](https://docs.python.org/3/library/functions.html#int)) – Specifies how often a block consisting of a rotation layer and entanglement layer is repeated.
- **seed** ([*int*](https://docs.python.org/3/library/functions.html#int) *| None*) – The seed for randomly choosing the axes of the Pauli rotations.
- **insert\_barriers** ([*bool*](https://docs.python.org/3/library/functions.html#bool)) – If `True`, barriers are inserted in between each layer. If `False`, no barriers are inserted. Defaults to `False`.
- **name** ([*str*](https://docs.python.org/3/library/stdtypes.html#str)) –

## Attributes

### num\_parameters\_settable

Return the number of settable parameters.

**Returns**

The number of possibly distinct parameters.

### name

Type: `str`

A human-readable name for the circuit.

**Example**

```python
from qiskit import QuantumCircuit

qc = QuantumCircuit(2, 2, name="my_circuit")
print(qc.name)
```

```text
my_circuit
```