Microwave-Transparent Infrared Filters for Superconducting Qubits

Infrared light traveling down coaxial cables can impact a superconducting quantum device, generating quasiparticle excitations and causing decoherence in superconducting qubits. Typically, this infrared radiation is suppressed by coaxial filters with a lossy Eccosorb dielectric. However, Eccosorb also strongly attenuates wanted microwave signals. We have investigated methods to suppress infrared radiation without unduly attenuating microwave signals. We present experimental and numerical results for filters based on alternative materials (including STYCAST 2850FT and borosilicate glass), resonant effects, and alternative geometries.