Unitary Subharmonic Response and Floquet Majorana Modes

TL;DR

This paper links the existence of Majorana fermions in topological systems to a subharmonic response phenomenon under periodic driving, proposing a method for their detection and stabilization using current quantum hardware.

Contribution

It introduces the concept that Majorana modes exhibit a subharmonic response in driven systems and demonstrates how disorder can stabilize this response for potential quantum computing applications.

Findings

Majorana modes show spin oscillations with twice the driving period.

Disorder can stabilize the subharmonic response of Majorana modes.

The phenomenon can be observed in superconducting circuits and cold atomic systems.

Abstract

Detection and manipulation of excitations with non-Abelian statistics, such as Majorana fermions, are essential for creating topological quantum computers. To this end, we show the connection between the existence of such localized particles and the phenomenon of unitary subharmonic response (SR) in periodically driven systems. In particular, starting from highly nonequilibrium initial states, the unpaired Majorana modes exhibit spin oscillations with twice the driving period, are localized, and can have exponentially long lifetimes in clean systems. While the lifetime of SR is limited in translationally invariant systems, we show that disorder can be engineered to stabilize the subharmonic response of Majorana modes. A viable observation of this phenomenon can be achieved using modern multiqubit hardware, such as superconducting circuits and cold atomic systems.