Scalable Quantum i/o: Integrated Cryogenic Microwave Components in Flexible Stripline Structures*

Conventional coaxial connectivity solutions for quantum computing have limited scaling potential towards and beyond the kQbit era due to cost, connection-density, form-factor and heat-load. In this work, we present a monolithic, multilayer, flexible circuit, which directly connects room temperature electronics to a milliKelvin interface of a quantum device. Specifically, we show the feasibility of scaling towards the kQubit era and beyond by integrating microwave filtering components inside of the flexible substrate. We also present a combination of planar low-pass and infra-red filters that maintains a noise-floor limited stop-band up to 50GHz, suitable for conditioning thermal noise in the millikelvin range. Finally, we address the thermalization of an integrated attenuator, which prevents unwanted localized thermal noise sources present in conventional attenuator solutions.