Feature Request: Adding Phase Gadgets

[y-richie-y]

Is there an easy way of adding a phase gadget to a graph / circuit?

[jvdwetering]

For Circuits there is the gate type ParityPhase, that acts as a phase-gadget on the specified set of qubits. There is no straightforward way right now to add a phase-gadget to a Graph other than adding the two vertices yourself. It might indeed be a good idea to add an easy function to do that though.