qpe_toolbox.circuit.custom_gates
================================

.. py:module:: qpe_toolbox.circuit.custom_gates

.. autoapi-nested-parse::

   Custom two-qubit gates registered with quimb's gate registry.



Functions
---------

.. autoapisummary::

   qpe_toolbox.circuit.custom_gates.su4swap_gate_param_gen
   qpe_toolbox.circuit.custom_gates.register_su4swap_gate


Module Contents
---------------

.. py:function:: su4swap_gate_param_gen(params)

   Return the ``SU4SWAP`` gate array, a general two-qubit gate rooted at identity.

   Equivalent to swapping the two output legs of quimb's 15-parameter ``SU4`` gate,
   so it tends to the identity as its parameters go to zero. It spans the same
   manifold as ``SU4`` (a subset of U(4)) and carries a free phase, so its
   determinant is not 1 (not literally an SU(4) gate).

   :param params: The 15 real parameters of the underlying ``SU4`` gate.
   :type params: array_like

   :returns: The gate as a ``(2, 2, 2, 2)`` array, on the same backend as ``params``.
   :rtype: array_like


.. py:function:: register_su4swap_gate()

   Register the ``SU4SWAP`` gate with quimb's gate registry, if not already present.