Paint it Black – To Protect the Qubits

Abstract

This thesis deals with reducing quasiparticle generation in superconducting circuits caused by stray photons by utilizing electromagnetic absorbers. This thesis deals with reducing quasiparticle generation in superconducting circuits caused by stray photons by utilizing electromagnetic absorbers. Quasiparticle generation is a known problem in several superconducting circuit applications such as quantum computing research. In order to quantify successful radiation reduction, a superconducting resonator was used as a sensor and a cylindrical shield was designed for testing the absorbers. Four different absorbers were tested, three of them are commercially available microwave absorbers and one was designed by our group. Internal differences were observed between the absorbers, however, compared to reference measurements, no improvements were observed. The results also indicates that the resonators properties changed in-between measurements and more tests should be performed in order to draw final conclusions.