Theoretical study of nonreciprocal microwave transmission based on Gebhard-Ruckenstein hopping

Several types of quantum information processing schemes and many of superconducting quantum optics experiments require routing of microwaves in a cryostat. Thus, cryogenic circulator is an important tool, and the loss at the circulators is detrimental especially for quantum information processing. This has been urging many researchers to experimental and theoretical works devoted to lossless on-chip microwave circulators.
In this presentation, we theoretically investigate the nonreciprocal microwave transmission based on the Gebhard-Ruckenstein hopping. We consider a superconducting device that consists of microwave resonators and a coupler. The Gebhard-Ruckenstein hopping between the resonators gives rise to a linear energy dispersion, which manifests chiral propagation of microwaves in the device. This device can work as a microscopic circulator when transmission lines are attached. It is shown that our microwave circulator can be robust against detuning of incident microwaves.