qiskit/releasenotes/notes/0.17/improve-clifford-synthesis-...

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---
features:
- |
The :func:`~qiskit.quantum_info.decompose_clifford` function in the
:mod:`~qiskit.quantum_info` module (which gets used internally by the
:meth:`qiskit.quantum_info.Clifford.to_circuit` method) has a new kwarg
``method`` which enables selecting the synthesis method used by either
setting it to ``'AG'`` or ``'greedy'``. By default for more than three
qubits it is set to ``'greedy'`` which uses a non-optimal greedy compilation
routine for Clifford elements synthesis, by Bravyi et. al., which typically
yields better CX cost compared to the previously used Aaronson-Gottesman
method (for more than two qubits). You can use the ``method`` kwarg to revert
to the previous default Aaronson-Gottesman method by setting ``method='AG'``.
upgrade:
- |
The default synthesis method used by
:func:`~qiskit.quantum_info.decompose_clifford` function in the
:mod:`~qiskit.quantum_info` module (which gets used internally by the
:meth:`qiskit.quantum_info.Clifford.to_circuit` method) for more than
3 qubits now uses a non-optimal greedy compilation routine for Clifford
elements synthesis, by Bravyi et. al., which typically yields better CX
cost compared to the old default. If you need to revert to the previous
Aaronson-Gottesman method this can be done by setting ``method='AG'``.