def circuit(w, x=None):
    qml.RX(w, wires=[0])
    qml.RX(x, wires=[1])
    return (qml.expval(qml.PauliZ(0)), qml.expval(qml.PauliZ(1)))
def circuit(w, x=None):
    qml.RX(w, wires=[0])
    qml.RX(x, wires=[1])
    return (qml.expval(qml.PauliZ(0)), qml.expval(qml.PauliZ(1)))