Curator's Take
AI Commentary
This article demonstrates the first gatemon qubits built from in‑situ grown ternary InAsSb/Al nanowire Josephson junctions, showing that compositionally engineered semiconductors can be combined with epitaxial superconductivity while retaining gate‑tunable microwave frequencies and coherence times on the order of a microsecond. By achieving T1 and T2* comparable to existing Al/InAs gatemons and revealing a clear frequency‑dependent relaxation consistent with spontaneous emission, the work validates the ternary weak link as a viable building block for scalable hybrid circuits. The ability to tailor band structure and carrier density through Sb alloying opens new design space for higher‑frequency qubits and potentially better integration with semiconductor platforms, marking a concrete step toward more versatile superconducting‑semiconductor quantum processors.
— Mark Eatherly
Summary
Ternary InAsSb/Al nanowires combine compositionally engineerable semiconductor properties with epitaxial proximity superconductivity, making them attractive for hybrid quantum circuits and mesoscopic superconductivity. Here, we realize gatemon qubits based on shadow-defined in-situ InAsSb/Al Josephson junctions in a single growth process. Gate-dependent microwave spectroscopy demonstrates electrostatic tuning of the qubit transition over several gigahertz. Rabi oscillations and Ramsey interference show coherent qubit control, with representative values T1 = 0.79 us and T2* = 0.91 us. Across five gatemons distributed over three chips, the measured relaxation times range from approximately 0.2 us to 1 us and decrease with increasing qubit frequency. Their magnitude is comparable to a circuit estimate of spontaneous emission into the electromagnetic environment. These results establish in-situ InAsSb/Al junctions as coherent, gate-tunable circuit elements and introduce cQED architecture as a microwave probe of the dynamics of the ternary weak link.