qiskit_aer.noise.NoiseModel.from_backend

classmethod NoiseModel.from_backend(backend, gate_error=True, readout_error=True, thermal_relaxation=True, temperature=0, gate_lengths=None, gate_length_units='ns', standard_gates=None, warnings=None)

Return a noise model derived from a devices backend properties.

This function generates a noise model based on:

• 1 and 2 qubit gate errors consisting of a depolarizing_error() followed by a thermal_relaxation_error().

• Single qubit ReadoutError on all measurements.

The error (noise) 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.

Note that if un-physical parameters are supplied, they are internally truncated to the theoretical bound values. For example, if \(T_2 > 2 T_1\), \(T_2\) parameter will be truncated to \(2 T_1\).

Additional Information

The noise model includes the following errors:

• If readout_error=True include single qubit readout errors on measurements.

• If gate_error=True and thermal_relaxation=True include:

  • Single-qubit gate errors consisting of a depolarizing_error() followed by a thermal_relaxation_error() for the qubit the gate acts on.

  • Two-qubit gate errors consisting of a 2-qubit depolarizing_error() followed by single qubit thermal_relaxation_error() on each qubit participating in the gate.

• If gate_error=True is True and thermal_relaxation=False:

  • An N-qubit depolarizing_error() on each N-qubit gate.

• If gate_error=False and thermal_relaxation=True include single-qubit thermal_relaxation_errors() on each qubits participating in a multi-qubit gate.

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

Specifying custom gate times

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.

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

Parameters

• backend (Backend) – backend. For BackendV2, standard_gates and warnings options are ignored, and their default values are used.

• gate_error (bool) – Include depolarizing gate errors (Default: True).

• readout_error (Bool) – Include readout errors in model (Default: True).

• thermal_relaxation (Bool) – Include thermal relaxation errors (Default: True).

• temperature (double) – qubit temperature in milli-Kelvin (mK) for thermal relaxation errors (Default: 0).

• gate_lengths (list) – Custom gate times for thermal relaxation errors. Used to extend or override the gate times in the backend properties (Default: None))

• gate_length_units (str) – Time units for gate length values in gate_lengths. Can be ‘ns’, ‘ms’, ‘us’, or ‘s’ (Default: ‘ns’).

• standard_gates (bool) – DEPRECATED, If true return errors as standard qobj gates. If false return as unitary qobj instructions (Default: None)

• warnings (bool) – PLAN TO BE DEPRECATED, Display warnings (Default: None).

Returns

An approximate noise model for the device backend.

Return type

NoiseModel

Raises

NoiseError – If the input backend is not valid.