@qml.qnode(qubit_device_2_wires, interface='tf')
def circuit_tf(phi, theta):
    qml.RX(phi[0], wires=0)
    qml.RY(phi[1], wires=1)
    qml.CNOT(wires=[0, 1])
    qml.PhaseShift(theta[0], wires=0)
    return qml.expval(qml.PauliZ(0))
@qml.qnode(qubit_device_2_wires, interface='tf')
def circuit_tf(phi, theta):
    qml.RX(phi[0], wires=0)
    qml.RY(phi[1], wires=1)
    qml.CNOT(wires=[0, 1])
    qml.PhaseShift(theta[0], wires=0)
    return qml.expval(qml.PauliZ(0))