318 lines
15 KiB
Plaintext
318 lines
15 KiB
Plaintext
---
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title: NoiseModel
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description: API reference for qiskit.providers.aer.noise.NoiseModel
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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.providers.aer.noise.NoiseModel
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---
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# NoiseModel
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<Class id="qiskit.providers.aer.noise.NoiseModel" isDedicatedPage={true} github="https://github.com/qiskit/qiskit-aer/tree/stable/0.9/qiskit/providers/aer/noise/noise_model.py" signature="NoiseModel(basis_gates=None)" modifiers="class">
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Bases: `object`
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Noise model class for Qiskit Aer simulators.
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This class is used to represent noise model for the [`QasmSimulator`](qiskit.providers.aer.QasmSimulator "qiskit.providers.aer.QasmSimulator"). It can be used to construct custom noise models for simulator, or to automatically generate a basic device noise model for an IBMQ backend. See the [`noise`](aer_noise#module-qiskit.providers.aer.noise "qiskit.providers.aer.noise") module documentation for additional information.
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**Example: Basic device noise model**
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An approximate [`NoiseModel`](#qiskit.providers.aer.noise.NoiseModel "qiskit.providers.aer.noise.NoiseModel") can be generated automatically from the properties of real device backends from the IBMQ provider using the [`from_backend()`](qiskit.providers.aer.noise.NoiseModel#from_backend "qiskit.providers.aer.noise.NoiseModel.from_backend") method.
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```python
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from qiskit import IBMQ, Aer
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from qiskit.providers.aer.noise import NoiseModel
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provider = IBMQ.load_account()
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backend = provider.get_backend('ibmq_vigo')
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noise_model = NoiseModel.from_backend(backend)
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print(noise_model)
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```
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**Example: Custom noise model**
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Custom noise models can be used by adding [`QuantumError`](qiskit.providers.aer.noise.QuantumError "qiskit.providers.aer.noise.QuantumError") to circuit gate, reset or measure instructions, and [`ReadoutError`](qiskit.providers.aer.noise.ReadoutError "qiskit.providers.aer.noise.ReadoutError") to measure instructions.
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```python
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import qiskit.providers.aer.noise as noise
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# Error probabilities
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prob_1 = 0.001 # 1-qubit gate
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prob_2 = 0.01 # 2-qubit gate
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# Depolarizing quantum errors
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error_1 = noise.depolarizing_error(prob_1, 1)
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error_2 = noise.depolarizing_error(prob_2, 2)
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# Add errors to noise model
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noise_model = noise.NoiseModel()
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noise_model.add_all_qubit_quantum_error(error_1, ['rz', 'sx', 'x'])
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noise_model.add_all_qubit_quantum_error(error_2, ['cx'])
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print(noise_model)
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```
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Initialize an empty noise model.
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**Parameters**
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**basis\_gates** (*list\[str] or None*) – Specify an initial basis\_gates for the noise model. If None a default value of \[‘id’, ‘rz’, ‘sx’, ‘cx’] is used (Default: None).
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Additional Information: Errors added to the noise model will have their instruction appended to the noise model basis\_gates if the instruction is in the [`QasmSimulator`](qiskit.providers.aer.QasmSimulator "qiskit.providers.aer.QasmSimulator") basis\_gates. If the instruction is not in the [`QasmSimulator`](qiskit.providers.aer.QasmSimulator "qiskit.providers.aer.QasmSimulator") basis\_gates it is assumed to be a label for a standard gate, and that gate should be added to the NoiseModel basis\_gates either using the init method, or the [`add_basis_gates()`](qiskit.providers.aer.noise.NoiseModel#add_basis_gates "qiskit.providers.aer.noise.NoiseModel.add_basis_gates") method.
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## Methods
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### add\_all\_qubit\_quantum\_error
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<Function id="qiskit.providers.aer.noise.NoiseModel.add_all_qubit_quantum_error" signature="NoiseModel.add_all_qubit_quantum_error(error, instructions, warnings=True)">
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Add a quantum error to the noise model that applies to all qubits.
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**Parameters**
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* **error** ([*QuantumError*](qiskit.providers.aer.noise.QuantumError "qiskit.providers.aer.noise.QuantumError")) – the quantum error object.
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* \*\*(****str**** or ****list****\[****str****] \*\***or** (*instructions*) – Instruction or list\[Instruction]): the instructions error applies to.
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* **warnings** (*bool*) – Display warning if appending to an instruction that already has an error (Default: True).
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**Raises**
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**NoiseError** – if the input parameters are invalid.
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#### Additional Information:
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If the error object is ideal it will not be added to the model.
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</Function>
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### add\_all\_qubit\_readout\_error
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<Function id="qiskit.providers.aer.noise.NoiseModel.add_all_qubit_readout_error" signature="NoiseModel.add_all_qubit_readout_error(error, warnings=True)">
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Add a single-qubit readout error that applies measure on all qubits.
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**Parameters**
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* **error** ([*ReadoutError*](qiskit.providers.aer.noise.ReadoutError "qiskit.providers.aer.noise.ReadoutError")) – the quantum error object.
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* **warnings** (*bool*) – Display warning if appending to an instruction that already has an error (Default: True)
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**Raises**
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**NoiseError** – if the input parameters are invalid.
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#### Additional Information:
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If the error object is ideal it will not be added to the model.
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</Function>
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### add\_basis\_gates
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<Function id="qiskit.providers.aer.noise.NoiseModel.add_basis_gates" signature="NoiseModel.add_basis_gates(instructions, warnings=True)">
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Add additional gates to the noise model basis\_gates.
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This should be used to add any gates that are identified by a custom gate label in the noise model.
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**Parameters**
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* \*\*(****list****\[****str****] \*\***or** (*instructions*) – list\[Instruction]): the instructions error applies to.
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* **warnings** (*bool*) – display warning if instruction is not in QasmSimulator basis\_gates (Default: True).
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</Function>
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### add\_nonlocal\_quantum\_error
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<Function id="qiskit.providers.aer.noise.NoiseModel.add_nonlocal_quantum_error" signature="NoiseModel.add_nonlocal_quantum_error(error, instructions, qubits, noise_qubits, warnings=True)">
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Add a non-local quantum error to the noise model (DEPRECATED).
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<Admonition title="Deprecated since version 0.9.0" type="danger">
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Adding nonlocal noise to a noise model is deprecated and will be removed no earlier than 3 months from the qiskit-aer 0.9.0 release date. To add non-local noise to a circuit you should write a custom qiskit transpiler pass.
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</Admonition>
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**Parameters**
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* **error** ([*QuantumError*](qiskit.providers.aer.noise.QuantumError "qiskit.providers.aer.noise.QuantumError")) – the quantum error object.
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* \*\*(****str**** or ****list****\[****str****] \*\***or** (*instructions*) – Instruction or list\[Instruction]): the instructions error applies to.
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* **qubits** (*list\[int]*) – qubits instruction error applies to.
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* **noise\_qubits** (*list\[int]*) – Specify the exact qubits the error should be applied to if different to the instruction qubits.
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* **warnings** (*bool*) – Display warning if appending to an instruction that already has an error (Default: True).
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**Raises**
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**NoiseError** – if the input parameters are invalid.
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#### Additional Information:
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If the error object is ideal it will not be added to the model.
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</Function>
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### add\_quantum\_error
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<Function id="qiskit.providers.aer.noise.NoiseModel.add_quantum_error" signature="NoiseModel.add_quantum_error(error, instructions, qubits, warnings=True)">
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Add a quantum error to the noise model.
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**Parameters**
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* **error** ([*QuantumError*](qiskit.providers.aer.noise.QuantumError "qiskit.providers.aer.noise.QuantumError")) – the quantum error object.
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* \*\*(****str**** or ****list****\[****str****] \*\***or** (*instructions*) – Instruction or list\[Instruction]): the instructions error applies to.
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* **qubits** (*list\[int]*) – qubits instruction error applies to.
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* **warnings** (*bool*) – Display warning if appending to an instruction that already has an error (Default: True).
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**Raises**
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**NoiseError** – if the input parameters are invalid.
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#### Additional Information:
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If the error object is ideal it will not be added to the model.
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</Function>
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### add\_readout\_error
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<Function id="qiskit.providers.aer.noise.NoiseModel.add_readout_error" signature="NoiseModel.add_readout_error(error, qubits, warnings=True)">
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Add a readout error to the noise model.
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**Parameters**
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* **error** ([*ReadoutError*](qiskit.providers.aer.noise.ReadoutError "qiskit.providers.aer.noise.ReadoutError")) – the quantum error object.
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* **qubits** (*list\[int]*) – qubits instruction error applies to.
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* **warnings** (*bool*) – Display warning if appending to an instruction that already has an error \[Default: True]
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**Raises**
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**NoiseError** – if the input parameters are invalid.
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#### Additional Information:
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If the error object is ideal it will not be added to the model.
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</Function>
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### from\_backend
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<Function id="qiskit.providers.aer.noise.NoiseModel.from_backend" signature="NoiseModel.from_backend(backend, gate_error=True, readout_error=True, thermal_relaxation=True, temperature=0, gate_lengths=None, gate_length_units='ns', standard_gates=True, warnings=True)" modifiers="classmethod">
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Return a noise model derived from a devices backend properties.
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This function generates a noise model based on:
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* 1 and 2 qubit gate errors consisting of a [`depolarizing_error()`](qiskit.providers.aer.noise.depolarizing_error "qiskit.providers.aer.noise.depolarizing_error") followed by a [`thermal_relaxation_error()`](qiskit.providers.aer.noise.thermal_relaxation_error "qiskit.providers.aer.noise.thermal_relaxation_error").
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* Single qubit [`ReadoutError`](qiskit.providers.aer.noise.ReadoutError "qiskit.providers.aer.noise.ReadoutError") on all measurements.
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The Error error parameters are tuned for each individual qubit based on the $T_1$, $T_2$, frequency and readout error parameters for each qubit, and the gate error and gate time parameters for each gate obtained from the device backend properties.
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**Additional Information**
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The noise model includes the following errors:
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* If `readout_error=True` include single qubit readout errors on measurements.
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* If `gate_error=True` and `thermal_relaxation=True` include:
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> * Single-qubit gate errors consisting of a [`depolarizing_error()`](qiskit.providers.aer.noise.depolarizing_error "qiskit.providers.aer.noise.depolarizing_error") followed by a [`thermal_relaxation_error()`](qiskit.providers.aer.noise.thermal_relaxation_error "qiskit.providers.aer.noise.thermal_relaxation_error") for the qubit the gate acts on.
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> * Two-qubit gate errors consisting of a 2-qubit [`depolarizing_error()`](qiskit.providers.aer.noise.depolarizing_error "qiskit.providers.aer.noise.depolarizing_error") followed by single qubit [`thermal_relaxation_error()`](qiskit.providers.aer.noise.thermal_relaxation_error "qiskit.providers.aer.noise.thermal_relaxation_error") on each qubit participating in the gate.
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* If `gate_error=True` is `True` and `thermal_relaxation=False`:
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> * An N-qubit [`depolarizing_error()`](qiskit.providers.aer.noise.depolarizing_error "qiskit.providers.aer.noise.depolarizing_error") on each N-qubit gate.
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* If `gate_error=False` and `thermal_relaxation=True` include single-qubit `thermal_relaxation_errors()` on each qubits participating in a multi-qubit gate.
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For best practice in simulating a backend make sure that the circuit is compiled using the set of basis gates in the noise module by setting `basis_gates=noise_model.basis_gates` and using the device coupling map with `coupling_map=backend.configuration().coupling_map`
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**Specifying custom gate times**
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The `gate_lengths` kwarg can be used to specify custom gate times to add gate errors using the $T_1$ and $T_2$ values from the backend properties. This should be passed as a list of tuples `gate_lengths=[(name, value), ...]` where `name` is the gate name string, and `value` is the gate time in nanoseconds.
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If a custom gate is specified that already exists in the backend properties, the `gate_lengths` value will override the gate time value from the backend properties. If non-default values are used gate\_lengths should be a list
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**Parameters**
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* **backend** ([*Backend*](qiskit.providers.Backend "qiskit.providers.Backend") *or*[*BackendProperties*](qiskit.providers.models.BackendProperties "qiskit.providers.models.BackendProperties")) – backend properties.
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* **gate\_error** (*bool*) – Include depolarizing gate errors (Default: True).
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* **readout\_error** (*Bool*) – Include readout errors in model (Default: True).
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* **thermal\_relaxation** (*Bool*) – Include thermal relaxation errors (Default: True).
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* **temperature** (*double*) – qubit temperature in milli-Kelvin (mK) for thermal relaxation errors (Default: 0).
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* **gate\_lengths** (*list*) – Custom gate times for thermal relaxation errors. Used to extend or override the gate times in the backend properties (Default: None))
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* **gate\_length\_units** (*str*) – Time units for gate length values in gate\_lengths. Can be ‘ns’, ‘ms’, ‘us’, or ‘s’ (Default: ‘ns’).
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* **standard\_gates** (*bool*) – If true return errors as standard qobj gates. If false return as unitary qobj instructions (Default: True)
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* **warnings** (*bool*) – Display warnings (Default: True).
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**Returns**
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An approximate noise model for the device backend.
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**Return type**
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[NoiseModel](qiskit.providers.aer.noise.NoiseModel "qiskit.providers.aer.noise.NoiseModel")
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**Raises**
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**NoiseError** – If the input backend is not valid.
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</Function>
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### from\_dict
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<Function id="qiskit.providers.aer.noise.NoiseModel.from_dict" signature="NoiseModel.from_dict(noise_dict)" modifiers="static">
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Load NoiseModel from a dictionary.
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**Parameters**
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**noise\_dict** (*dict*) – A serialized noise model.
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**Returns**
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the noise model.
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**Return type**
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[NoiseModel](qiskit.providers.aer.noise.NoiseModel "qiskit.providers.aer.noise.NoiseModel")
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**Raises**
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**NoiseError** – if dict cannot be converted to NoiseModel.
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</Function>
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### is\_ideal
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<Function id="qiskit.providers.aer.noise.NoiseModel.is_ideal" signature="NoiseModel.is_ideal()">
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Return True if the noise model has no noise terms.
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</Function>
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### reset
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<Function id="qiskit.providers.aer.noise.NoiseModel.reset" signature="NoiseModel.reset()">
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Reset the noise model.
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</Function>
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### to\_dict
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<Function id="qiskit.providers.aer.noise.NoiseModel.to_dict" signature="NoiseModel.to_dict(serializable=False)">
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Return the noise model as a dictionary.
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**Parameters**
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**serializable** (*bool*) – if True, return a dict containing only types that can be serializable by the stdlib json module.
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**Returns**
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a dictionary for a noise model.
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**Return type**
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dict
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</Function>
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## Attributes
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### basis\_gates
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<Attribute id="qiskit.providers.aer.noise.NoiseModel.basis_gates">
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Return basis\_gates for compiling to the noise model.
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</Attribute>
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### noise\_instructions
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<Attribute id="qiskit.providers.aer.noise.NoiseModel.noise_instructions">
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Return the set of noisy instructions for this noise model.
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</Attribute>
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### noise\_qubits
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<Attribute id="qiskit.providers.aer.noise.NoiseModel.noise_qubits">
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Return the set of noisy qubits for this noise model.
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</Attribute>
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</Class>
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