Double quantum dot with integrated charge sensor based on Ge/Si heterostructure nanowires

TL;DR

This paper demonstrates a Ge/Si heterostructure nanowire-based double quantum dot with an integrated charge sensor, advancing solid-state spin qubits by reducing hyperfine interactions and enabling precise charge detection.

Contribution

It introduces a fully tunable double quantum dot and a novel charge sensing method in Ge/Si nanowires, improving qubit coherence prospects.

Findings

Successful fabrication of a top gate-defined double quantum dot in Ge/Si nanowires.

Implementation of a capacitive charge sensor via an adjacent nanowire dot.

Potential for high-coherence spin qubits due to reduced hyperfine interactions.

Abstract

Coupled electron spins in semiconductor double quantum dots hold promise as the basis for solid-state qubits. To date, most experiments have used III-V materials, in which coherence is limited by hyperfine interactions. Ge/Si heterostructure nanowires seem ideally suited to overcome this limitation: the predominance of spin-zero nuclei suppresses the hyperfine interaction and chemical synthesis creates a clean and defect-free system with highly controllable properties. Here we present a top gate-defined double quantum dot based on Ge/Si heterostructure nanowires with fully tunable coupling between the dots and to the leads. We also demonstrate a novel approach to charge sensing in a one-dimensional nanostructure by capacitively coupling the double dot to a single dot on an adjacent nanowire. The double quantum dot and integrated charge sensor serve as an essential building block required to form a solid-state spin qubit free of nuclear spin.