Control and detection of Majorana bound states in quantum dot arrays

TL;DR

This study investigates how quantum dot arrays coupled to superconductors can host and manipulate Majorana bound states, revealing conditions under which well-separated Majorana zero modes can be stabilized for potential quantum computing applications.

Contribution

The paper demonstrates that potential wells in quantum dot arrays can trap Majorana pairs, leading to stable zero modes, and provides detailed numerical analysis of their emergence and control.

Findings

Multiple low-energy sub-gap states emerge near uncovered regions.

Zero-bias conductance peaks can occur without well-separated Majoranas.

Potential wells can trap and stabilize Majorana pairs.

Abstract

We study the low-energy physics of a one-dimensional array of superconducting quantum dots realized by proximity coupling a semiconductor nanowire to multiple superconducting islands separated by narrow uncovered regions. The effective electrostatic potential inside the quantum dots and the uncovered regions can be controlled using potential gates. By performing detailed numerical calculations based on effective tightbinding models, we find that multiple low-energy sub-gap states consisting of partially overlapping Majorana bound states emerge generically in the vicinity of the uncovered regions. Explicit differential conductance calculations show that a robust zero-bias conductance peak is not inconsistent with the presence of such states localized throughout the system, hence the observation of such a peak does not demonstrate the realization of well-separated Majorana zero modes. However, we find that creating effective potential wells in the uncovered regions traps pairs of nearby partially overlapping Majorana bound states, which become less separated and acquire a finite gap that protects the pair of Majorana zero modes localized at the ends of the system. This behavior persists over a significant parameter range, suggesting that proximitized quantum dot arrays could provide a platform for highly controllable Majorana devices.