Tunable Resonant and Nonresonant Interactions between a Phase Qubit and LC Resonator
Michael S. Allman, Jed D. Whittaker, Manuel C. Castellanos Beltran, Katarina Cicak, Fabio C. Da Silva, Michael DeFeo, Florent Q. Lecocq, Adam J. Sirois, John D. Teufel, Jose A. Aumentado, Raymond W. Simmonds
We use a flux-biased radio frequency superconducting quantum interference device (rf SQUID) with an embedded flux-biased direct current SQUID to generate strong resonant and nonresonant tunable interactions between a phase qubit and a lumped-element resonator. The rf SQUID creates a tunable magnetic susceptibility between the qubit and resonator providing resonant coupling strengths from zero to near the ultrastrong coupling regime. By modulating the magnetic susceptibility, nonresonant parametric coupling achieves rates > 100 MHz. Nonlinearity of the magnetic susceptibility also leads to parametric coupling at the subharmonics of the qubit-resonator detuning.