Tunable coupling of transmission-line microwave resonators mediated by an rf SQUID

Abstract

We realize tunable coupling between two superconducting transmission line resonators. The coupling is mediated by a non-hysteretic rf SQUID acting as a flux-tunable mutual inductance between the resonators. We present a spectroscopic characterization of the device. In particular, we observe couplings $g/2\pi$ ranging between −320 MHz and 37 MHz. In the case of $g \simeq 0$ , the microwave power cross transmission between the two resonators is reduced by almost four orders of magnitude as compared to the case where the coupling is switched on.