Synthesizing Directionality in Parametric Circuits

José Aumentado

National Institute of Standards and Technology, Boulder

Parametric amplifiers have had an enormous impact on superconducting quantum computing, providing a means to assess the state of complex multi-qubit circuits quickly. However, basic reflection parametric amplifiers rely on a simple two-mode coupling scheme that produces a reciprocal gain response at the input and output frequencies, requiring the use of lossy circulators that reduce quantum efficiency as well as occupy valuable real estate in a dilution refrigerator. In this talk, I will discuss a recent approach to generating directionality (nonreciprocity) in circuits by parametrically coupling multiple modes to produce circulation and directional gain. This approach has several advantages, including the elimination of intervening circulators, but also in the ability to directly integrate quantum-limited amplifiers with the circuits that they measure. We demonstrate this by measuring a transmon with a prototype amplifier directly connected to a 3D readout cavity.