Abstract: We have developed a superconducting transmon qubit with a semiconductor-based Josephson junction element [1,2]. The junction is made from an InAs nanowire with in situ molecular beam epitaxy-grown superconducting Al contacts. This gate-controlled transmon, or gatemon, allows simple tuning of the qubit transition frequency using a gate voltage to vary the density of carriers in the semiconductor region. In the first generations of devices we have measured coherence times up to 10 µs. These coherence times, combined with stable qubit operation, permit single qubit rotations with fidelities of ~99.5% for all gates including voltage-controlled Z rotations. Towards multi-qubit operation we have also implemented a two qubit voltage-controlled cPhase gate. In contrast to flux-tuned transmons, voltage-tunable gatemons may simplify the task of scaling to multi-qubit circuits and enable new means of control for many qubit architectures.
 T. W. Larsen et al., Phys. Rev. Lett. 115, 127001 (2015).
 G. de Lange et al., Phys. Rev. Lett. 115, 127002 (2015).