add-group-commuting-method-in-PauliList-and-SparsePauliOp-5dec2877c4a97861.yaml

---
features:
  - |
    Added the methods :meth:`.PauliList.group_commuting` and :meth:`.SparsePauliOp.group_commuting`,
    which partition these operators into sublists where each element commutes with all the others.
    For example::

      from qiskit.quantum_info import PauliList, SparsePauliOp

      groups = PauliList(["XX", "YY", "IZ", "ZZ"]).group_commuting()
      # 'groups' is [PauliList(['IZ', 'ZZ']), PauliList(['XX', 'YY'])]

      op = SparsePauliOp.from_list([("XX", 2), ("YY", 1), ("IZ", 2j), ("ZZ", 1j)])
      groups = op.group_commuting()
      # 'groups' is [
      #     SparsePauliOp(['IZ', 'ZZ'], coeffs=[0.+2.j, 0.+1.j]),
      #     SparsePauliOp(['XX', 'YY'], coeffs=[2.+0.j, 1.+0.j]),
      # ]