Reviving Majorana zero modes in the spin-1/2 Kitaev ladder model

TL;DR

This paper proposes a method to revive and manipulate Majorana zero modes in the spin-1/2 Kitaev ladder model by selecting specific $Z_2$ flux sectors and applying local spin operators, advancing topological quantum computation.

Contribution

It introduces a projective measurement technique to select $Z_2$ sectors, enabling the revival and control of Majorana modes in the Kitaev ladder system.

Findings

Majorana modes can be revived by sector selection.

Local spin operators can manipulate flux sectors.

Majorana modes can be fused and controlled.

Abstract

The one-dimensional $p$-wave superconductor, characterized by boundary Majorana modes, has attracted significant interest owing to its potential application in topological quantum computation. Similarly, spin-1/2 Kitaev ladder systems with bond-dependent Ising interactions, featuring Majorana fermions coupled with $Z_2$ flux, exhibit boundary Majorana modes when in a topological phase. However, the ground state degeneracy, inherent in these systems, may result in the annihilation of Majorana modes due to the superposition of the degenerate states. To avoid this issue, here we introduce a projective measurement that selects one of the degenerate $Z_2$ sectors, enabling the revival of Majorana modes. Once the state is selected, we show that the application of the local spin operators on a bond flips the sign of the adjacent $Z_2$ flux. Repeating such operators enables the system to reach a desired $Z_2$ flux configuration. The Majorana zero modes can be manipulated and fused by tuning the flux sectors achievable through applying local spin operators. We also discuss the engineering of the Kitaev ladder and open questions for future studies.