Minimal Models for Nonreciprocal Amplification Using Biharmonic Drives

Detection and efficient readout of weak signals in the quantum regime are critical aspects of quantum information processing. Current measurement protocols rely on amplifiers plus signal routers (circulators or isolators), but bulk is problematic for any scalable architecture. The authors present minimal, efficient schemes to design nonreciprocal quantum-limited amplifiers for simultaneous routing and boosting of signals. This could lead to significantly simpler measurement chains, which is especially relevant in the face of increasingly complex multi-qubit experiments.