Fast Broadband Superconducting Microwave Switches Based on Artificial Transmission Lines

As superconducting computing systems continue to scale, the demand for efficient multiplexing of microwave lines becomes increasingly critical. In particular, a fast, broadband, low loss, solid-state, and ultra–low-power microwave switch capable of operating at millikelvin temperatures is highly desirable. We propose a design for such a device based on a tunable artificial transmission line composed of SQUID inductors shunted by capacitors. In the “on” state, the SQUID inductance is tuned to realize an effective 50 Ω transmission line. In the “off” state, the SQUIDs are tuned near frustration, thereby lowering the line cutoff frequency and creating a wide stopband with exponential attenuation.

We simulate the impact of fabrication and bias disorder and find the device to be compatible with current fabrication technology. Using this idea, designs for switches with up to 4 ports are shown.