Low-Dissipation Multiplexed Flux-Sensitive Readout in Superconducting Circuits

D-Wave's quantum processors require a high-fidelity readout architecture for fast and accurate operation. The need for cold operation precludes readout methods with significant dissipation. The readout architecture must be scalable and compatible with an inherently dense qubit circuit layout. Superconducting microresonators have been successfully utilized as detection elements for a wide variety of applications, enabling superior multiplexing factors. In existing designs, resonators undergo a non-uniform shift in frequency and sensitivity with fabrication imperfections, ultimately limiting effective bandwidth utilization. We overcome this drawback by implementing independent control of both frequency and sensitivity. We describe the design of the detector and report experimental results demonstrating its resilience to fabrication tolerances.