One of the Quaracter project goals is to compare the microwave and thermal performance of Cri/oFlex® wiring to its conventional coaxial counterpart. Several companies worked in close collaboration to build and evaluate the system. Delft Circuits provided the cryogenic i/o for control and readout, Orange QS acted as a systems integrator and supplied their control software, and Leiden Cryogenics provided the dilution refrigerator. A transmon-based quantum processor was used. The project is co-sponsored by the Zuid-Holland province of the Netherlands.
Cri/oFlex® microwave drive line was installed from room temperature down to the mK stage to interface the qubits. The drive line included the following configuration of the integrated filtering: -20 dB attenuator located at 100 mK and 10 mK stages, -10 dB attenuator at 4 K, low-pass filter with a cutoff frequency of 8 GHz located at 100 mK stage, infrared filter with the slope of -1 dB/GHz located below 10 mK stage.
The coaxial cabling configuration included commercially available Stainless Steel wiring, a low-pass filter with a cutoff frequency of 8 GHz, and three attenuators of -20 dB each.
The transmission loss measured at room temperature for both configurations is shown in the figure. The comparison of conventional coaxial cable (in blue) and Delft Circuits Cri/oFlex® (in orange) shows that flexible RF cabling is a potential replacement for coax solutions. The project is continuing with the evaluation of the qubit performance using different I/O solutions.