Designing qubit circuits

It’s hard work being the only postdoc in the village. One day I’m fixing wiring on the fridge, the next I’m analysing the effect of spin-flip scattering on my superconductor-ferromagnet data. Today I’m being the local RSFQ/SQUID layout afficionado.

I’m designing some qubit circuits. Process design rules are a pain, there are about 10 layers in a Standard Niobium process and you have to get all the holes and structures spaced correctly (do I hear a tiny violin?). Luckily I have several helpful guides such as Ustinov’s group website, which contains information (mostly in the doctoral theses) on their structures which were fabricated by VTT and HYPRES.

Here are some pictures of what I’m doing:



They are very preliminary designs at the moment, I haven’t even got all the layers in there yet.
I also have to calculate the mutual inductances between the structures using finite element techniques, which lets you know how well your qubit couples to your readout circuitry (In this case, DC SQUIDs and microwave resonators, depending on the design). It’s quite fun to do circuit layout though. These circuits will probably be realised at the European FLUXONICS foundry at IPHT.


3 thoughts on “Designing qubit circuits

  1. Paul B. says:

    Wow, Suz! Kic? πŸ˜‰ Painful, painful memories…

    If you install any modern Fedora with Electronic Lab ( you will get several a bit more decent, or at least recent free layout editors (toped, Alliance, and, of course, good old magic).

    Or talk to your Uni. EE department to see if they have Campus-wide Cadence licenses — Cadence used to offer unlimited licenses for everything to universities for, like, $5000/year (creating market for $50,000/year per seat per license when students graduate and go into industry).

    Good luck!

    Paul B.

    • physicsandcake says:


      I’m surprised anyone recognised the interface πŸ˜€

      Originally I was using EasyCAD, so KIC actually seemed like quite a welcome change πŸ˜‰ (KIC is the only thing I have that can write to GDS).

      I’ll have a look at some more modern open source stuff. The problem is with buying site licenses (apart from all the fuss that we have to go through) is that we only do layouts about once or twice a year… but I would like to learn Cadence anyway so I’ll see if I can get a group of interested people together and look into that!

  2. dark_daedalus says:

    I haven’t used them in anger, but I think the following are good, free and can read and write GDS :

    You might also want to have a look in the database at :

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s