Robust Strong-Coupling Architecture in Circuit Quantum Electrodynamics

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We report on a robust method to achieve strong coupling between a superconducting flux qubit and a high-quality quarter-wavelength coplanar waveguide resonator. We demonstrate the progression from the strong to ultrastrong coupling regime by varying the length of a shared inductive coupling element, ultimately achieving a qubit-resonator coupling strength of 655 MHz, 10% of the resonator frequency. We derive an analytical expression for the coupling strength in terms of circuit parameters and also discuss the maximum achievable coupling within this framework. We experimentally characterize flux qubits coupled to superconducting resonators using one- and two-tone spectroscopy methods, demonstrating excellent agreement with the proposed theoretical model.

Original languageEnglish
Article number044045
Number of pages11
JournalPhysical Review Applied
Issue number4
Publication statusPublished - 25 Oct 2021
MoE publication typeA1 Journal article-refereed


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