text: import numpy as np
  
  from qutip.qip.circuit import QubitCircuit, Gate
  from qutip.qip.compiler import GateCompiler, Instruction
  
  
  __all__ = ['CavityQEDCompiler']
  
  
  class CavityQEDCompiler(GateCompiler):
      """
      Decompose a :class:`.QubitCircuit` into
      the pulse sequence for the processor.
  
      Parameters
      ----------
      N: int
          The number of qubits in the system.
  
      params: dict
          A Python dictionary contains the name and the value of the parameters.
          See :meth:`.DispersiveCavityQED.set_up_params` for the definition.
  
      global_phase: float, optional
          Record of the global phase change and will be returned.
  
      pulse_dict: dict, optional
          A map between the pulse label and its index in the pulse list.
          If given, the compiled pulse can be identified with
          ``(pulse_label, coeff)``, instead of ``(pulse_index, coeff)``.
          The number of key-value pairs should match the number of pulses
          in the processor.
          If it is empty, an integer ``pulse_index`` needs to be used
          in the compiling routine saved under the attributes ``gate_compiler``.
  
      Attributes
      ----------
      N: int
          The number of the component systems.
  
      params: dict
          A Python dictionary contains the name and the value of the parameters,
          such as laser frequency, detuning etc.
  
      pulse_dict: dict
          A map between the pulse label and its index in the pulse list.
  
      gate_compiler: dict
          The Python dictionary in the form of {gate_name: decompose_function}.
          It saves the decomposition scheme for each gate.
      """
      def __init__(self, N, params, pulse_dict, global_phase=0.):
          super(CavityQEDCompiler, self).__init__(
              N=N, params=params, pulse_dict=pulse_dict)
          self.gate_compiler.update({
              "ISWAP": self.iswap_compiler,
              "SQRTISWAP": self.sqrtiswap_compiler,
              "RZ": self.rz_compiler,
              "RX": self.rx_compiler,
              "GLOBALPHASE": self.globalphase_compiler
              })
          self.wq = np.sqrt(self.params["eps"]**2 + self.params["delta"]**2)
          self.Delta = self.wq - self.params["w0"]
          self.global_phase = global_phase
  
      def rz_compiler(self, gate, args):
          """
          Compiler for the RZ gate
          """
          targets = gate.targets
          g = self.params["sz"][targets[0]]
          coeff = np.sign(gate.arg_value) * g
          tlist = abs(gate.arg_value) / (2 * g)
          pulse_info = [("sz" + str(targets[0]), coeff)]
          return [Instruction(gate, tlist, pulse_info)]
  
      def rx_compiler(self, gate, args):
          """
          Compiler for the RX gate
          """
          targets = gate.targets
          g = self.params["sx"][targets[0]]
          coeff = np.sign(gate.arg_value) * g
          tlist = abs(gate.arg_value) / (2 * g)
          pulse_info = [("sx" + str(targets[0]), coeff)]
          return [Instruction(gate, tlist, pulse_info)]
  
      def sqrtiswap_compiler(self, gate, args):
          """
          Compiler for the SQRTISWAP gate
  
          Notes
          -----
          This version of sqrtiswap_compiler has very low fidelity, please use
          iswap
          """
          # FIXME This decomposition has poor behaviour
          q1, q2 = gate.targets
          pulse_info = []
          pulse_name = "sz" + str(q1)
          coeff = self.wq[q1] - self.params["w0"]
          pulse_info += [(pulse_name, coeff)]
          pulse_name = "sz" + str(q1)
          coeff = self.wq[q2] - self.params["w0"]
          pulse_info += [(pulse_name, coeff)]
          pulse_name = "g" + str(q1)
          coeff = self.params["g"][q1]
          pulse_info += [(pulse_name, coeff)]
          pulse_name = "g" + str(q2)
          coeff = self.params["g"][q2]
          pulse_info += [(pulse_name, coeff)]
  
          J = self.params["g"][q1] * self.params["g"][q2] * (
              1 / self.Delta[q1] + 1 / self.Delta[q2]) / 2
          tlist = (4 * np.pi / abs(J)) / 8
          instruction_list = [Instruction(gate, tlist, pulse_info)]
  
          # corrections
          gate1 = Gate("RZ", [q1], None, arg_value=-np.pi/4)
          compiled_gate1 = self.rz_compiler(gate1, args)
          instruction_list += compiled_gate1
          gate2 = Gate("RZ", [q2], None, arg_value=-np.pi/4)
          compiled_gate2 = self.rz_compiler(gate2, args)
          instruction_list += compiled_gate2
          gate3 = Gate("GLOBALPHASE", None, None, arg_value=-np.pi/4)
          self.globalphase_compiler(gate3, args)
          return instruction_list
  
      def iswap_compiler(self, gate, args):
          """
          Compiler for the ISWAP gate
          """
          q1, q2 = gate.targets
          pulse_info = []
          pulse_name = "sz" + str(q1)
          coeff = self.wq[q1] - self.params["w0"]
          pulse_info += [(pulse_name, coeff)]
          pulse_name = "sz" + str(q2)
          coeff = self.wq[q2] - self.params["w0"]
          pulse_info += [(pulse_name, coeff)]
          pulse_name = "g" + str(q1)
          coeff = self.params["g"][q1]
          pulse_info += [(pulse_name, coeff)]
          pulse_name = "g" + str(q2)
          coeff = self.params["g"][q2]
          pulse_info += [(pulse_name, coeff)]
  
          J = self.params["g"][q1] * self.params["g"][q2] * (
              1 / self.Delta[q1] + 1 / self.Delta[q2]) / 2
          tlist = (4 * np.pi / abs(J)) / 4
          instruction_list = [Instruction(gate, tlist, pulse_info)]
  
          # corrections
          gate1 = Gate("RZ", [q1], None, arg_value=-np.pi/2.)
          compiled_gate1 = self.rz_compiler(gate1, args)
          instruction_list += compiled_gate1
          gate2 = Gate("RZ", [q2], None, arg_value=-np.pi/2)
          compiled_gate2 = self.rz_compiler(gate2, args)
          instruction_list += compiled_gate2
          gate3 = Gate("GLOBALPHASE", None, None, arg_value=-np.pi/2)
          self.globalphase_compiler(gate3, args)
          return instruction_list
  
      def globalphase_compiler(self, gate, args):
          """
          Compiler for the GLOBALPHASE gate
          """
          self.global_phase += gate.arg_value
  