code: def _param_su2(ar: float, ai: float, br: float, bi: float):
      """
      Create a matrix in the SU(2) form from complex parameters a, b.
      The resulting matrix is not guaranteed to be in SU(2), unless |a|^2 + |b|^2 = 1.
      """
      return np.array(
          [[ar + 1j * ai, -br + 1j * bi], [br + 1j * bi, ar + 1j * -ai]]
      )
  
file_path: pennylane/pennylane/ops/op_math/controlled_decompositions.py
imports: from copy import copy
  import numpy
  import numpy.linalg
  import pennylane
  from pennylane.operation import Operator
  from pennylane.wires import Wires
  from pennylane import math
label_desc: Use image node_id 3 for calling a global function with example usage: _param_su2(ar, ai, br, bi) and returns: np