Super-Poissonian noise from quasiparticle poisoning in electron transport through a pair of Majorana bound states

TL;DR

This paper investigates how quasiparticle poisoning influences electron transport through Majorana bound states, revealing super-Poissonian noise signatures that can aid in detecting MBSs despite poisoning effects.

Contribution

It demonstrates that quasiparticle poisoning induces super-Poissonian shot noise in MBS transport, emphasizing the importance of including next-to-leading order tunneling in models.

Findings

QPP causes diverging Fano factor at low bias voltage

Super-Poissonian noise is a key signature of MBSs under QPP

Current and non-local noise are minimally affected by QPP

Abstract

Topological qubits based on non-abelian Majorana bound states (MBSs) are protected by parity which is challenged by quasiparticle poisoning (QPP). In this work, we show how QPP affects transport through a pair of coupled MBSs weakly connected to two current leads, using an open system approach and full counting statistics. We find that the correct low-energy physics requires to include next to leading order tunneling events in the coupling to the leads. In particular, our results show that QPP causes super-Poissonian local shot noise with a Fano factor that diverges with decreasing bias voltage, while the current and the non-local (cross-)noise are only little affected. We explain that these features are a direct consequence of the nature of MBSs being their own antiparticle making noise measurements a viable tool to search for MBSs in the presence of QPP.