Superconducting gatemon qubit based on a proximitized two-dimensional electron gas*

The nonlinear inductance generated by Josephson junctions (JJs) is used extensively in quantum information processors based on superconducting circuits. The inductance is either fixed by the metal-oxide dimensions of a single JJ, or magnetically tuned using a superconducting quantum interference device with current-biased flux lines. One tantalizing all-electric alternative are superconductor-semiconductor hybrid JJs with gate-tuneable critical currents. Gatemons have demonstrated the feasibility of this approach using nanowire JJs to control superconducting qubits in the transmon regime [1, 2]. Here we demonstrate that semiconducting channels etched from a wafer-scale two-dimensional electron gas (2DEG) are a natural platform for building a truly scalable gatemon-based universal quantum computer. We show 2DEG gatemons meet the requirements by performing arbitrary voltage-controlled rotations around the Bloch sphere and two-qubit swap operations. We measure qubit lifetimes up to ~2 us, limited by dielectric loss in the 2DEG host substrate.
[1] G. de Lange et al., PRL 115, 127002 (2015); [2] Larsen et al., PRL 115, 127001 (2015).