Nonreciprocal Microwave Signal Processing with a Field-Programmable Josephson Amplifier

The authors program a superconducting circuit $i\phantom{\rule{0}{0ex}}n$ $s\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}u$ to operate as a microwave circulator, or a directional amplifier. The compact lumped element can be directly integrated with other superconducting circuitry for nearly lossless routing and measurement of quantum microwave signals. This work combines advanced understanding of parametric-coupling physics with innovative design and engineering, for fundamental impact on quantum measurements plus direct technological impact on current efforts to build scalable, on-chip infrastructure for quantum computing.