Gate-Tunable Transmon Using Selective-Area-Grown Superconductor-Semiconductor Hybrid Structures on Silicon

We present a gate-voltage-tunable transmon qubit (gatemon) based on planar InAs nanowires that are selectively grown on a high-resistivity silicon substrate using III-V buffer layers. We show that low-loss superconducting resonators with an internal quality of 2×10⁵ can readily be realized using these substrates after the removal of buffer layers. We demonstrate coherent control and readout of a gatemon device with a relaxation time, T₁≈7000.2em0exns, and dephasing times, T₂^≈200.2em0exns and T2,echo≈1.30.2em0exμs. Further, we infer a high junction transparency of $0.4$--$0.9$ from an analysis of the qubit anharmonicity.