Flexible Coaxial Ribbon Cable for High-Density Superconducting Microwave Device Arrays

Superconducting electronics often require high-density microwave interconnects capable of transporting signals between temperature stages with minimal loss, cross talk, and heat conduction. We report the design fabrication superconducting 53 wt% Nb-47 Ti (Nb47Ti) FLexible coAXial ribbon cables (FLAX). The ten traces each consist a 0.076 mm O.D. NbTi inner conductor insulated PFA (0.28 O.D.) sheathed in shared 0.025 thick Nb47Ti outer conductor. cable is terminated G3PO coaxial push-on connectors via stainless steel capillary tubing (1.6 O.D., 0.13 thick) soldered to coplanar wave guide transition board. 30 cm long has 1 dB loss at 8 GHz -60 nearest-neighbor forward talk. 0.5 more than commercially available coax likely due impedance mismatches caused by manufacturing imperfections cable. reported talk lower previously developed laminated NbTi-onKapton microstrip cables. estimate load from K 90 mK be 20 nW per trace, approximately half computed smallest CryoCoax