Variable Delay Superconducting Transmission Line

We have developed a variable delay microwave transmission line using the Josephson inductance of RF-SQUIDs as a nonlinear magnetic medium. We couple up to 180,000 Nb SQUIDs to a microstrip line. The resulting device acts both as a true time delay phase shifter from dc to 20 GHz, and also as a wideband parametric upconverting amplifier. As a phase shifter, we observe up to 1 nanosecond variable delay in a single 5-mm chip. As a parametric amplifier, we observe a transimpedance gain of 5000 ohms and up to 1 GHz bandwidth. Bandwidth, dynamic range, and noise temperature are all significant improvements over earlier superconducting amplifiers.