Infrared Filters for Superconducting Qubit Applications

Superconducting qubits are manipulated and read out using microwave signals which are generated at room temperature and guided through coaxial cables to the milikelvin temperature stage. One common problem of coax cables is their high transparency to infrared radiation originating from a rather high photon flux sources at elevated temperatures
of cryostat stages. Filtering out the infrared radiation requires a lowpass filter with a sharp cutoff in the micro- or low mm-wave frequency range.
We present simulations as well as experimental data on a new generation of powder based filters. The samples are investigated over the full band of infrared radiation using conventional detectors as well as superconducting qubits directly.