Multiple ground plane thermal sink

A monolithic microwave integrated circuit (MMIC) comprising:

• a thermal sink layer underlying a substrate;
• a first electrically conducting ground plane associated with a first set of superconducting circuits that have a first operational temperature requirement;
• a first set of thermally conductive vias that each couple the first electrically conducting ground plane to the thermal sink layer through the substrate;
• a second electrically conducting ground plane associated with a second set of superconducting circuits that have a second operational temperature requirement that is higher than the first operational temperature requirement;
• a second set of thermally conductive vias that each couple the second ground plane to the thermal sink layer through the substrate, wherein the first set of thermally conductive vias removes a greater amount of heat from the first set of superconducting circuits than the second set of superconducting circuits.