Hole-type superconducting gatemon qubit based on Ge/Si core/shell nanowires

Abstract

Abstract We demonstrate that superconducting gatemon qubits based on superconductor-semiconductor-superconductor Josephson junctions can be constructed on hole-type Ge/Si core/shell nanowires. The frequency of the qubit can be set firstly by controlling the diffusion of Al in the nanowire via thermal annealing, which yields a suitable critical supercurrent allowing the qubit frequency to be within the experimentally accessible range, and then by fine tuning of a gate voltage, by which an accurate adjustment of the frequency can be realized. On the resulted qubit, Rabi oscillation with an energy relaxation time $${T}_{1} \sim 180\,{\rm{ns}}$$ T 1 ~ 180 ns was observed in the time domain, an average decoherence time $${T}_{2}^{* } \sim 15\,{\rm{ns}}$$ T 2 * ~ 15 ns was obtained, and the gate voltage dependence of both $${T}_{1}$$ T 1 and $${T}_{2}^{* }$$ T 2 * was investigated. Such a hole-type superconducting gatemon qubit, based on materials with strong spin-orbit coupling and potentially the absence of hyperfine interaction after isotope purification, could be used for exploring the quantum coherence phenomena of hole-gas and even Majorana physics in Ge-based quantum devices.