Masters Defense: Carlo Modica

Abstract

III-V semiconducting materials are a good platform for defining Superconductor-Semiconductor-Superconductor Josephson Junctions (JJ). The Josephson energy of such JJ can be tuned via an electrostatic gate: planar superconducting circuits can then be fabricated on III-V patterned with such JJ to make quantum processors.

III-V materials have piezoelectric proprieties; the electric field stored in the qubit capacitors can dissipate energy via phonons onto the substrate, adding an extra loss channel with respect to ordinary qubit capacitors fabricated on silicon. This thesis lays the foundations for the making of three-dimensional vacuum gap capacitors that ought to store the electric field of the qubit capacitors in vacuum, by creating a parallel plate capacitor in a flip-chip configuration. A reliable flip-chip fabrication process was defined, and used to fabricate 3D resonant LC circuit working in the qubits frequency range.