---
features:
  - |
    Added a new ``norm estimation`` method for performing measurements when using
    the `"extended_stabilizer"` simulation method. This norm estimation method
    can be used by passing the following options to the
    :class:`~qiskit.providers.aer.AerSimulator` and
    :class:`~qiskit.providers.aer.QasmSimulator` backends

    .. code::python

      simulator = QasmSimulator(
          method='extended_stabilizer',
          extended_stabilizer_sampling_method='norm_estimation')

    The norm estimation method is slower than the alternative `metropolis`
    or `resampled_metropolis` options, but gives better performance on circuits
    with sparse output distributions. See the documentation of the
    :class:`~qiskit.providers.aer.QasmSimulator` for more information.
fixes:
  - |
    Fixes an issue where the Extended `"extended_stabilizer"` simulation method
    would give incorrect results on quantum circuits with sparse output
    distributions. Refer to
    `#306 <https://github.com/Qiskit/qiskit-aer/issues/306>` for more
    information and examples.
upgrade:
  - |
    The following options for the `"extended_stabilizer"` simulation method
    have changed.

      + ``extended_stabilizer_measure_sampling``: This option has been replaced
        by the options ``extended_stabilizer_sampling_method``, which controls
        how we simulate qubit measurement.
      
      + ``extended_stabilizer_mixing_time``: This option has been renamed as
        ``extended_stabilizer_metropolis_mixing_time`` to clarify it only applies
        to the `metropolis` and `resampled_metropolis` sampling methods.
      
      + ``extended_stabilizer_norm_estimation_samples``: This option has been renamed
        to ``extended_stabilizer_norm_estimation_default_samples``.
     
    One additional option, ``extended_stabilizer_norm_estimation_repetitions`` has been
    added, whih controls part of the behaviour of the norm estimation sampling method.
