A gate tunable transmon qubit in planar Ge

Abstract

Gate-tunable transmons (gatemons) employing semiconductor Josephson junctions have recently emerged as building blocks for hybrid quantum circuits. In this study, we present a gatemon fabricated in planar Germanium. We induce superconductivity in a two-dimensional hole gas by evaporating aluminum atop a thin spacer, which separates the superconductor from the Ge quantum well. The Josephson junction is then integrated into an Xmon circuit and capacitively coupled to a transmission line resonator. We showcase the qubit tunability in a broad frequency range with resonator and two-tone spectroscopy. Time-domain characterizations reveal energy relaxation and coherence times up to 75 ns. Our results, combined with the recent advances in the spin qubit field, pave the way towards novel hybrid and protected qubits in a group IV, CMOS-compatible material.

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• Gatemonium: A Voltage-Tunable Fluxonium
• A Review of Design Concerns in Superconducting Quantum Circuits
• The carbon nanotube gatemon qubit
• Nonlinearity of transparent SNS weak links decreases sharply with length
• Superconducting Proximity Effect in Two-Dimensional Hole Gases
• Impact of surface treatments on the transport properties of germanium 2DHGs
• Integration of graphene-based superconducting quantum circuits in 3D cavity
• Theory of superconducting proximity effect in hole-based hybrid semiconductor-superconductor devices
• Gatemon Qubit Revisited for Improved Reliability and Stability
• Supercurrent and multiple Andreev reflections in Ge hut nanowire Josephson Junctions
• Determination of the current-phase relation of an InAs 2DEG Josephson junction with a microwave resonator
• Gate- and flux-tunable sin(2$\phi$) Josephson element with proximitized Ge-based junctions