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class TensoredMeasFitter(results, mit_pattern, substate_labels_list=None, circlabel='')

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Bases: object

Measurement correction fitter for a tensored calibration.

Initialize a measurement calibration matrix from the results of running the circuits returned by measurement_calibration_circuits.


This class is not a public API. The internals are not stable and will likely change. It is used solely for the measurement_error_mitigation_cls kwarg of the QuantumInstance class’s constructor (as a class not an instance). Anything outside of that usage does not have the normal user-facing API stability.


  • results – the results of running the measurement calibration circuits. If this is None, the user will set calibration matrices later.
  • mit_pattern (List[List[int]]) – qubits to perform the measurement correction on, divided to groups according to tensors
  • substate_labels_list (Optional[List[List[str]]]) – for each calibration matrix, the labels of its rows and columns. If None, the labels are ordered lexicographically
  • circlabel (str) – if the qubits were labeled


ValueError – if the mit_pattern doesn’t match the substate_labels_list



TensoredMeasFitter.add_data(new_results, rebuild_cal_matrix=True)

Add measurement calibration data


  • new_results (list or qiskit.result.Result) – a single result or list of Result objects.
  • rebuild_cal_matrix (bool) – rebuild the calibration matrix


TensoredMeasFitter.readout_fidelity(cal_index=0, label_list=None)

Based on the results, output the readout fidelity, which is the average of the diagonal entries in the calibration matrices.


  • cal_index (integer) – readout fidelity for this index in _cal_matrices
  • label_list (list) – Returns the average fidelity over of the groups f states. In the form of a list of lists of states. If None, then each state used in the construction of the calibration matrices forms a group of size 1


The readout fidelity (assignment fidelity)

Return type



QiskitError – If the calibration matrix has not been set for the object.

Additional Information:

The on-diagonal elements of the calibration matrices are the probabilities of measuring state ‘x’ given preparation of state ‘x’.



Return a fitter object that is a subset of the qubits in the original list.

This is only a partial implementation of the subset_fitter method since only mitigation patterns of length 1 are supported. This corresponds to patterns of the form [[0], [1], [2], ...]. Note however, that such patterns are a good first approximation to mitigate readout errors on large quantum circuits.


qubit_sublist (list) – must be a subset of qubit_list


A new fitter that has the calibration for a

subset of qubits

Return type



  • QiskitError – If the calibration matrix is not initialized
  • QiskitError – If the mit pattern is not a tensor of single-qubit measurement error mitigation.
  • QiskitError – If a qubit in the given qubit_sublist is not in the list of qubits in the mit. pattern.



Return cal_matrices.


Return a measurement filter using the cal matrices.


Return _qubit_list_sizes.


Return _substate_labels_list.

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