Project details

Context

Superconducting quantum devices, including qubits, are highly sensitive to various sources of noise which significantly affect their performance. Among these, thermal and magnetic noise are particularly critical, as they degrade the coherence time of the qubits. Over the past decades, substantial efforts have been made to shield the tunable transmon qubit from these types of noise. However, exploring alternative materials and fabrication processes remains an essential area of research to enhance superconducting circuit performance.

The project consists in the fabrication and characterization of superconducting qubit chips. With the goal of optimizing the manufacturing process to enhance reproducibility and internal quality factor of the resonators.

Results

Over the course of a semester, I explored a variety of cleanroom fabrication processes for making coplanar superconducting resonators, mainly using Niobium or Tantalum capped Niobium thin films. Most of the effort was directed towards the materials interfaces to minimize dielectric losses at low microwave power. To this extent various surface cleaning processes were investigated, both dry and wet, including notably forming gas and oxygen plasma as well as HF etching. Each device is then characterized in a dilution unit so as to monitor the effect on internal quality factors of the fabricated circuits.