Nonlocality of Majorana Modes in Hybrid Nanowires

TL;DR

This study experimentally measures the nonlocality of Majorana zero modes in superconductor-semiconductor nanowires, providing insights into their separation and spin properties crucial for topological quantum computing.

Contribution

It introduces a quantitative method to assess the nonlocality of Majorana modes via tunneling spectroscopy and quantum dot hybridization in nanowire devices.

Findings

Measured varying degrees of nonlocality, indicating partial to well-developed Majorana modes.

Extracted spin canting angles of the zero modes.

Identified conditions leading to highly nonlocal Majorana states.

Abstract

Spatial separation of Majorana zero modes distinguishes trivial from topological midgap states and is key to topological protection in quantum computing applications. Although signatures of Majorana zero modes in tunneling spectroscopy have been reported in numerous studies, a quantitative measure of the degree of separation, or nonlocality, of the emergent zero modes has not been reported. Here, we present results of an experimental study of nonlocality of emergent zero modes in superconductor-semiconductor hybrid nanowire devices. The approach takes advantage of recent theory showing that nonlocality can be measured from splitting due to hybridization of the zero mode in resonance with a quantum dot state at one end of the nanowire. From these splittings as well as anticrossing of the dot states, measured for even and odd occupied quantum dot states, we extract both the degree of nonlocality of the emergent zero mode, as well as the spin canting angles of the nonlocal zero mode. Depending on the device measured, we obtain either a moderate degree of nonlocality, suggesting a partially separated Andreev subgap state, or a highly nonlocal state consistent with a well-developed Majorana mode.