Multifrequency modes in superconducting resonators: Bridging frequency gaps in off-resonant couplings

Christian Kraglund Andersen; Klaus Mølmer

doi:10.1103/PhysRevA.91.023828

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Multifrequency modes in superconducting resonators: Bridging frequency gaps in off-resonant couplings

Christian Kraglund Andersen, Klaus Mølmer

DOI 10.1103/PhysRevA.91.023828 · Physical Review A

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Abstract

A superconducting quantum interference device (SQUID) inserted in a superconducting waveguide resonator imposes current and voltage boundary conditions that makes it suitable as a tuning element for the resonator modes. If such a SQUID element is subject to a periodically varying magnetic flux, the resonator modes acquire frequency sidebands. In this work we calculate the multifrequency eigenmodes of resonators coupled to periodically driven SQUIDs and we use the Lagrange formalism to propose a theory for their quantization. The elementary excitations of a multifrequency mode can couple resonantly to physical systems with different transition frequencies and this makes the resonator an efficient quantum bus for state transfer and coherent quantum operations in hybrid quantum systems. As an example of the application of our multifrequency modes, we determine their coupling to transmon qubits with different frequencies and we present a bichromatic scheme for entanglement and gate operations.