157 lines
12 KiB
Plaintext
157 lines
12 KiB
Plaintext
---
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title: noise
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description: API reference for qiskit.providers.aer.noise
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in_page_toc_min_heading_level: 2
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python_api_type: module
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python_api_name: qiskit.providers.aer.noise
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---
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<span id="module-qiskit.providers.aer.noise" />
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<span id="aer-noise" />
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# Noise Models
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<span id="module-qiskit.providers.aer.noise" />
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`qiskit.providers.aer.noise`
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This module contains classes and functions to build a noise model for simulating a Qiskit quantum circuit in the presence of errors.
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## Building Noise Models
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The [`NoiseModel`](qiskit.providers.aer.noise.NoiseModel "qiskit.providers.aer.noise.NoiseModel") 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, to to automatically generate a basic device noise model for an IBMQ backend.
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### Device Noise Models
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A simplified 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 [`NoiseModel.from_backend()`](qiskit.providers.aer.noise.NoiseModel#from_backend "qiskit.providers.aer.noise.NoiseModel.from_backend") method. See the method documentation for details.
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**Example: Basic device noise model**
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```python
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from qiskit import QuantumCircuit, execute
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from qiskit import IBMQ, Aer
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from qiskit.visualization import plot_histogram
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from qiskit.providers.aer.noise import NoiseModel
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# Build noise model from backend properties
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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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# Get coupling map from backend
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coupling_map = backend.configuration().coupling_map
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# Get basis gates from noise model
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basis_gates = noise_model.basis_gates
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# Make a circuit
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circ = QuantumCircuit(3, 3)
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circ.h(0)
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circ.cx(0, 1)
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circ.cx(1, 2)
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circ.measure([0, 1, 2], [0, 1, 2])
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# Perform a noise simulation
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result = execute(circ, Aer.get_backend('qasm_simulator'),
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coupling_map=coupling_map,
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basis_gates=basis_gates,
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noise_model=noise_model).result()
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counts = result.get_counts(0)
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plot_histogram(counts)
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```
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### Custom Noise Models
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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. This module includes several helper functions for generating [`QuantumError`](qiskit.providers.aer.noise.QuantumError "qiskit.providers.aer.noise.QuantumError") instances based on canonical error models used in Quantum Information Theory that can simplify building noise models. See the documentation for the [`NoiseModel`](qiskit.providers.aer.noise.NoiseModel "qiskit.providers.aer.noise.NoiseModel") class for additional details.
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**Example: depolarizing noise model**
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```python
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from qiskit import QuantumCircuit, execute, Aer
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from qiskit.visualization import plot_histogram
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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, ['u1', 'u2', 'u3'])
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noise_model.add_all_qubit_quantum_error(error_2, ['cx'])
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# Get basis gates from noise model
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basis_gates = noise_model.basis_gates
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# Make a circuit
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circ = QuantumCircuit(3, 3)
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circ.h(0)
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circ.cx(0, 1)
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circ.cx(1, 2)
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circ.measure([0, 1, 2], [0, 1, 2])
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# Perform a noise simulation
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result = execute(circ, Aer.get_backend('qasm_simulator'),
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basis_gates=basis_gates,
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noise_model=noise_model).result()
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counts = result.get_counts(0)
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plot_histogram(counts)
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```
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## Classes
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The following are the classes used to represented noise and error terms.
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| ------------------------------------------------------------------------------------------------------------------------------------------- | ----------------------------------------------- |
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| [`NoiseModel`](qiskit.providers.aer.noise.NoiseModel "qiskit.providers.aer.noise.NoiseModel")(\[basis\_gates]) | Noise model class for Qiskit Aer simulators. |
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| [`QuantumError`](qiskit.providers.aer.noise.QuantumError "qiskit.providers.aer.noise.QuantumError")(noise\_ops\[, number\_of\_qubits, ...]) | Quantum error class for Qiskit Aer noise model |
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| [`ReadoutError`](qiskit.providers.aer.noise.ReadoutError "qiskit.providers.aer.noise.ReadoutError")(probabilities\[, atol]) | Readout error class for Qiskit Aer noise model. |
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## Quantum Error Functions
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The following functions can be used to generate many common types of [`QuantumError`](qiskit.providers.aer.noise.QuantumError "qiskit.providers.aer.noise.QuantumError") objects for inclusion in a [`NoiseModel`](qiskit.providers.aer.noise.NoiseModel "qiskit.providers.aer.noise.NoiseModel").
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| ----------------------------------------------------------------------------------------------------------------------------------------------------------------------- | --------------------------------------------------------------------------------- |
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| [`pauli_error`](qiskit.providers.aer.noise.pauli_error "qiskit.providers.aer.noise.pauli_error")(noise\_ops\[, standard\_gates]) | Return a mixed Pauli quantum error channel. |
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| [`depolarizing_error`](qiskit.providers.aer.noise.depolarizing_error "qiskit.providers.aer.noise.depolarizing_error")(param, num\_qubits\[, ...]) | Return a depolarizing quantum error channel. |
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| [`pauli_error`](qiskit.providers.aer.noise.pauli_error "qiskit.providers.aer.noise.pauli_error")(noise\_ops\[, standard\_gates]) | Return a mixed Pauli quantum error channel. |
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| [`mixed_unitary_error`](qiskit.providers.aer.noise.mixed_unitary_error "qiskit.providers.aer.noise.mixed_unitary_error")(noise\_ops\[, standard\_gates]) | Return a mixed unitary quantum error channel. |
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| [`coherent_unitary_error`](qiskit.providers.aer.noise.coherent_unitary_error "qiskit.providers.aer.noise.coherent_unitary_error")(unitary) | Return a coherent unitary quantum error channel. |
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| [`reset_error`](qiskit.providers.aer.noise.reset_error "qiskit.providers.aer.noise.reset_error")(prob0\[, prob1]) | Return a single qubit reset quantum error channel. |
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| [`amplitude_damping_error`](qiskit.providers.aer.noise.amplitude_damping_error "qiskit.providers.aer.noise.amplitude_damping_error")(param\_amp\[, ...]) | Return a single-qubit generalized amplitude damping quantum error channel. |
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| [`phase_damping_error`](qiskit.providers.aer.noise.phase_damping_error "qiskit.providers.aer.noise.phase_damping_error")(param\_phase\[, ...]) | Return a single-qubit generalized phase damping quantum error channel. |
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| [`phase_amplitude_damping_error`](qiskit.providers.aer.noise.phase_amplitude_damping_error "qiskit.providers.aer.noise.phase_amplitude_damping_error")(param\_amp, ...) | Return a single-qubit combined phase and amplitude damping quantum error channel. |
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| [`thermal_relaxation_error`](qiskit.providers.aer.noise.thermal_relaxation_error "qiskit.providers.aer.noise.thermal_relaxation_error")(t1, t2, time\[, ...]) | Return a single-qubit thermal relaxation quantum error channel. |
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| [`kraus_error`](qiskit.providers.aer.noise.kraus_error "qiskit.providers.aer.noise.kraus_error")(noise\_ops\[, standard\_gates, ...]) | Return a Kraus quantum error channel. |
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## Noise Transpiler Passes
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These transpiler passes can be used to build noise models that can be applied to circuits via transpilation.
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| ---------------------------------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------- |
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| [`LocalNoisePass`](qiskit.providers.aer.noise.LocalNoisePass "qiskit.providers.aer.noise.LocalNoisePass")(func\[, op\_types, method]) | Transpiler pass to insert noise into a circuit. |
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| [`RelaxationNoisePass`](qiskit.providers.aer.noise.RelaxationNoisePass "qiskit.providers.aer.noise.RelaxationNoisePass")(t1s, t2s\[, dt, ...]) | Add duration dependent thermal relaxation noise after instructions. |
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## Device Noise Parameters
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The following are utility functions which can be used for extracting error parameters and error objects from device BackendProperties.
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| --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | -------------------------------------------------------------------- |
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| [`device.basic_device_readout_errors`](qiskit.providers.aer.noise.device.basic_device_readout_errors "qiskit.providers.aer.noise.device.basic_device_readout_errors")(properties) | Return readout error parameters from a devices BackendProperties. |
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| [`device.basic_device_gate_errors`](qiskit.providers.aer.noise.device.basic_device_gate_errors "qiskit.providers.aer.noise.device.basic_device_gate_errors")(properties) | Return QuantumErrors derived from a devices BackendProperties. |
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| [`device.gate_param_values`](qiskit.providers.aer.noise.device.gate_param_values "qiskit.providers.aer.noise.device.gate_param_values")(properties) | Return parameter error values from a devices BackendProperties. |
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| [`device.gate_error_values`](qiskit.providers.aer.noise.device.gate_error_values "qiskit.providers.aer.noise.device.gate_error_values")(properties) | Return gate error values from a devices BackendProperties. |
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| [`device.gate_length_values`](qiskit.providers.aer.noise.device.gate_length_values "qiskit.providers.aer.noise.device.gate_length_values")(properties) | Return gate length values from a devices BackendProperties. |
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| [`device.readout_error_values`](qiskit.providers.aer.noise.device.readout_error_values "qiskit.providers.aer.noise.device.readout_error_values")(properties) | Return readout error values from a devices BackendProperties. |
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| [`device.thermal_relaxation_values`](qiskit.providers.aer.noise.device.thermal_relaxation_values "qiskit.providers.aer.noise.device.thermal_relaxation_values")(properties) | Return T1, T2 and frequency values from a devices BackendProperties. |
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