code: def ghz_circuit(qubits: Qubits) -> Circuit:
      
      circ = Circuit()
  
      circ += H(qubits[0])
      for q0 in range(0, len(qubits)-1):
          circ += CNOT(qubits[q0], qubits[q0+1])
  
      return circ
docs: Returns a circuit that prepares a multi-qubit Bell state from the zero
      state.