Coupling strength between superconducting transmon qubit and mode of electromagnetic field in 3D microwave cavity

Abstract

We investigate the coupling strength between a superconducting qubit and two different electromagnetic modes (TE101 and TE201) in the 3D cavity. Since the spontaneous decay of qubit depends on the coupling to the resonant mode of the cavity (the Purcell effect), the qubit relaxation depends not only on TE101(in case that the qubit is positioned in the middle of the cavity) but also on other adjacent higher order modes that couples to the qubit. In this study, we performed numerical simulations and measurements of the coupling strength of a qubit that is coupled to multiple modes. We also examined the dependence of the coupling strength on the position of the qubit in the cavity. This result is a crucial parameter in designing a circuit QED system for quantum information processing.