Two-photon coupling via Josephson element: Breaking the symmetry with magnetic fields

E. V. Stolyarov; V. L. Andriichuk; A. M. Sokolov

doi:10.1103/w12t-92qg

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Two-photon coupling via Josephson element: Breaking the symmetry with magnetic fields

E. V. Stolyarov, V. L. Andriichuk, A. M. Sokolov

DOI 10.1103/w12t-92qg · Physical Review B

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Abstract

We consider a coupling element based on a symmetric superconducting quantum interference device (SQUID) and show that it mediates a two-photon interaction. This and other inductive interactions due to the SQUID can be switched off in situ. We derive the system Hamiltonian for a coupled resonator and rf SQUID. The rf SQUID dwells in the vicinity of its metastable well holding a number of energy states and acts as an artificial atom. We discuss how the Josephson symmetry breaks owing to magnetic fields in the superconducting loops—both directly and via a nonzero superconducting phase difference over the rf SQUID. We assess that the two-photon coupling strength reaches 18 MHz which can exceed the single-photon capacitive interaction in the coupler.