JJ Help

[NxtGenLegend]

Hey! Do I need to add in a JJ to my TransmonCross for Palace eigenmodal Sims? Because currently I'm not able to

[PP501]

Yes - this is to make it flexible in the arrangement. Look at our examples. We add one of our Dolan Bridge JJs; in the simulation that JJ is just a rectangle that provides a lumped inductance.

[NxtGenLegend]

In which example? I've been referring to the capsim & eigensim in worked examples with the xmon & resonator, my aim is to run a transmoncross with a JJ for an eigensim & capsim

[PP501]

Hello; apologies for not realising that we had not added this example to the repository. I have amended it with a new worked example. Let me know if you have any issues. Note that:

• The path for Palace should be changed to your local path
• Adjust the minimum starting frequency (from which to search) accordingly to suit your design
• The JJ in the Dolan Bridge part must be specified via the create_port_JosephsonJunction command. Note that you must either supply the keyword argument L_J or E_J (i.e. Josephson inductance or the Josephson Junction energy). You can also optionally supply the junction capacitance C_J.

Let us know if you have any further issues

[NxtGenLegend]

Thank you! Where is the create_port_JosephsonJunction function? Also, to clarify, I replace JunctionDolanPinStretch with create_port_JosephsonJunction? Additionally, since I want to add a lumped inductance for a resistance of 50 ohms, the L_J & E_J param I assume can take care of that solely, or do I need to add in further code for those features? I ask because the current function in the new worked script essentially creates new geometries from my understanding, but with no inductance or resistance properties

[PP501]

Okay to clarify, the workflow to add a JJ is:

• You create the geometry as required for lithography. Some parts like the JunctionDolanPinStretch have a special rectangle that represents the simulation construct to create an effective port excitation
• Now to let Palace know what port properties to give this JJ, we must use create_port_JosephsonJunction

Thus, you first create the JJ part (note that some qiskit metal Transmon parts come equipped with the special rectangle) such as JunctionDolanPinStretch. Then you endow it with the properties via create_port_JosephsonJunction. You can find the example in the script as:

eigen_sim.create_port_JosephsonJunction('junction', L_J=4.3e-9, C_J=10e-15)

So you can either specify L_J or E_J to specify the mandatory inductance. You can then specify C_J for the optional JJ capacitance.

Now to add a normal RF port such as a $50\Omega$ feed (with resistance, inductance, capacitance etc.), you use create_port_CPW_on_Launcher as in this example. There are other ones like create_port_CPW_on_Route and create_port_2_conds_by_position. We will document properly those soon.