Transmission phase read-out of a large quantum dot in a nanowire interferometer

TL;DR

This paper demonstrates the first interferometric measurement of the transmission phase of a quantum dot in a nanowire, revealing phase lapses and interference effects crucial for topological qubit read-out.

Contribution

It introduces a nanowire-based interferometric setup for phase measurement of quantum dots, advancing the understanding of electron transport in topological quantum systems.

Findings

Observation of Fano resonances indicating quantum interference

Detection of phase lapses between Fano peaks

Insights into multi-path interference effects

Abstract

Detecting the transmission phase of a quantum dot via interferometry can reveal the symmetry of the orbitals and details of electron transport. Crucially, interferometry will enable the read-out of topological qubits based on one-dimensional nanowires. However, measuring the transmission phase of a quantum dot in a nanowire has not yet been established. Here, we exploit recent breakthroughs in the growth of one-dimensional networks and demonstrate interferometric read-out in a nanowire-based architecture. In our two-path interferometer, we define a quantum dot in one branch and use the other path as a reference arm. We observe Fano resonances stemming from the interference between electrons that travel through the reference arm and undergo resonant tunnelling in the quantum dot. Between consecutive Fano peaks, the transmission phase exhibits phase lapses that are affected by the presence of multiple trajectories in the interferometer. These results provide critical insights for the design of future topological qubits.