Modular and compact designs for multi-qubit devices in 2D and 3D cQED architecture

Although not highly scalable, the 3D cQED architecture provides a more modular design for few qubit devices. On the other hand, the 2D architecture lacks modularity since both qubit and resonators are defined on a single chip. This often puts stringent requirements on the fabrication of 2D chips as variability in Josephson junction parameters can render the entire chip unusable.
Here, we introduce a modular cQED design for medium scale circuits in both 2D and 3D architecture by combining modularity with a compact design. In 2D, modularity is introduced by making the qubit devices on a separate chip from the resonators. The qubit chips, like surface mount components can then be integrated with the resonator chip by employing a form of chip to chip bonding technique. In the 3D architecture, the rectangular/coaxial cavities can be replaced by compact designs similar to planar CPW geometries. This allows us to choose the best qubit chips for integration with the rest of the microwave circuit. We will show results from finite-element EM simulations for both these designs and explain how one can optimize the design parameters. We will also present preliminary experimental data and explain how we can build different types of multi-qubit devices using these ideas.