Getting more information about a circuit

In the previous section, we used the QuantumCircuit class’s count_ops function to find out whether Alice applies an X gate and whether the circuit has an even or odd number of Hadamard gates. Sometimes, you need to discover more details about an existing circuit. For cases of this kind, you can use the QuantumCircuit class’s data attribute. A circuit’s data attribute contains enough information to recreate the circuit in its entirety. Take, for example, the circuit shown in Figure 5.21:

Figure 5.21 – The smallest circuit returned by any call to make_new_circuit

If you print this circuit’s data attribute, and you add your own line breaks, you will see the following information:

[  CircuitInstruction(
    operation=Instruction(
      name='swap', num_qubits=2, num_clbits=0, params=[]
    ...