Strong coupling between cavity and flopping-mode qubit beyond direct gate connection in a Si/SiGe triple quantum dot

Abstract

Cavity coupled flopping-mode spin qubit is considered as a promising scheme for enabling long-range qubit interactions in large-scale semiconductor quantum computation. In this work, we fabricate a linear Si/SiGe triple quantum dot (TQD) array coupled with a high-impedance TiN coplanar waveguide cavity via the gate of outer quantum dot. By utilizing two adjacent dots within the TQD, we sequentially encode two flopping-mode qubits at different positions, whether with or without gate connection, which exhibit strong coupling to the cavity. Furthermore, we demonstrate the qubit manipulation with the help of dispersive readout, achieving Rabi oscillation frequencies of 16.9 and 13.7 MHz at zero detuning. These results expand the spatial range of qubit coupling and readout via the cavity, enhancing the operational efficiency of cavity-quantum dot array coupled system.