73 lines
5.4 KiB
Plaintext
73 lines
5.4 KiB
Plaintext
---
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title: efficient_su2 (latest version)
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description: API reference for qiskit.circuit.library.efficient_su2 in the latest version of qiskit
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in_page_toc_min_heading_level: 1
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python_api_type: class
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python_api_name: qiskit.circuit.library.efficient_su2
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---
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<span id="efficient-su2" />
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# efficient\_su2
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<Class id="qiskit.circuit.library.efficient_su2" isDedicatedPage={true} github="https://github.com/Qiskit/qiskit/tree/stable/1.3/qiskit/circuit/library/n_local/efficient_su2.py#L31-L134" signature="qiskit.circuit.library.efficient_su2(num_qubits, su2_gates=None, entanglement='reverse_linear', reps=3, skip_unentangled_qubits=False, skip_final_rotation_layer=False, parameter_prefix='θ', insert_barriers=False, name='EfficientSU2')" modifiers="class">
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Bases:
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The hardware-efficient $SU(2)$ 2-local circuit.
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The `efficient_su2` circuit consists of layers of single qubit operations spanned by $SU(2)$ and CX entanglements. This is a heuristic pattern that can be used to prepare trial wave functions for variational quantum algorithms or classification circuit for machine learning.
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$SU(2)$ is the special unitary group of degree 2, its elements are $2 \times 2$ unitary matrices with determinant 1, such as the Pauli rotation gates.
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On 3 qubits and using the Pauli $Y$ and $Z$ rotations as single qubit gates, the this circuit is represented by:
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```python
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┌──────────┐┌──────────┐ ░ ░ ░ ┌───────────┐┌───────────┐
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┤ RY(θ[0]) ├┤ RZ(θ[3]) ├─░────────■───░─ ... ─░─┤ RY(θ[12]) ├┤ RZ(θ[15]) ├
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├──────────┤├──────────┤ ░ ┌─┴─┐ ░ ░ ├───────────┤├───────────┤
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┤ RY(θ[1]) ├┤ RZ(θ[4]) ├─░───■──┤ X ├─░─ ... ─░─┤ RY(θ[13]) ├┤ RZ(θ[16]) ├
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├──────────┤├──────────┤ ░ ┌─┴─┐└───┘ ░ ░ ├───────────┤├───────────┤
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┤ RY(θ[2]) ├┤ RZ(θ[5]) ├─░─┤ X ├──────░─ ... ─░─┤ RY(θ[14]) ├┤ RZ(θ[17]) ├
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└──────────┘└──────────┘ ░ └───┘ ░ ░ └───────────┘└───────────┘
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```
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**Examples**
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Per default, the `"reverse_linear"` entanglement is used, which, in the case of CX gates, is equivalent to an all-to-all entanglement:
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```python
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from qiskit.circuit.library import efficient_su2
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circuit = efficient_su2(3, reps=1)
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circuit.draw("mpl")
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```
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To specify which SU(2) gates should be used in the rotation layer, we can set the `su2_gates` argument. In addition, we can change the entanglement structure. For example:
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```python
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circuit = efficient_su2(4, su2_gates=["rx", "y"], entanglement="circular", reps=1)
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circuit.draw("mpl")
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```
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**Parameters**
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* **num\_qubits** ([*int*](https://docs.python.org/3/library/functions.html#int "(in Python v3.13)")) – The number of qubits.
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* **su2\_gates** ([*str*](https://docs.python.org/3/library/stdtypes.html#str "(in Python v3.13)") *|*[*Gate*](qiskit.circuit.Gate "qiskit.circuit.Gate") *| Iterable\[*[*str*](https://docs.python.org/3/library/stdtypes.html#str "(in Python v3.13)") *|*[*Gate*](qiskit.circuit.Gate "qiskit.circuit.Gate")*] | None*) – The $SU(2)$ single qubit gates to apply in single qubit gate layers. If only one gate is provided, the same gate is applied to each qubit. If a list of gates is provided, all gates are applied to each qubit in the provided order.
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* **reps** ([*int*](https://docs.python.org/3/library/functions.html#int "(in Python v3.13)")) – Specifies how often the structure of a rotation layer followed by an entanglement layer is repeated.
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* **entanglement** (*BlockEntanglement | Iterable\[BlockEntanglement] | Callable\[\[*[*int*](https://docs.python.org/3/library/functions.html#int "(in Python v3.13)")*], BlockEntanglement | Iterable\[BlockEntanglement]]*) – The indices specifying on which qubits the input blocks act. See `n_local()` for detailed information.
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* **skip\_final\_rotation\_layer** ([*bool*](https://docs.python.org/3/library/functions.html#bool "(in Python v3.13)")) – Whether a final rotation layer is added to the circuit.
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* **skip\_unentangled\_qubits** ([*bool*](https://docs.python.org/3/library/functions.html#bool "(in Python v3.13)")) – If `True`, the rotation gates act only on qubits that are entangled. If `False`, the rotation gates act on all qubits.
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* **parameter\_prefix** ([*str*](https://docs.python.org/3/library/stdtypes.html#str "(in Python v3.13)")) – The name of the free parameters.
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* **insert\_barriers** ([*bool*](https://docs.python.org/3/library/functions.html#bool "(in Python v3.13)")) – If True, barriers are inserted in between each layer. If False, no barriers are inserted.
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* **name** ([*str*](https://docs.python.org/3/library/stdtypes.html#str "(in Python v3.13)")) – The name of the circuit.
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**Returns**
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An efficient-SU(2) circuit.
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</Class>
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