Boosting Majorana zero modes

TL;DR

This paper analyzes the behavior of Majorana zero modes in one-dimensional topological superconductors when domain walls move at various velocities, revealing stability at subluminal speeds and dissolution at luminal or superluminal speeds, with implications for quantum computation.

Contribution

It provides an exact solution for the quasiparticle spectrum of moving domain walls, demonstrating the relativistic effects on Majorana modes and establishing velocity limits for braiding operations.

Findings

Majorana zero modes are stable below a critical velocity.

At luminal or superluminal speeds, Majorana modes dissolve into quasiparticles.

The results impose an upper limit on braiding frequencies in topological quantum computing.

Abstract

One-dimensional topological superconductors are known to host Majorana zero modes at domain walls terminating the topological phase. Their nonabelian nature allows for processing quantum information by braiding operations which are insensitive to local perturbations, making Majorana zero modes a promising platform for topological quantum computation. Motivated by the ultimate goal of executing quantum information processing on a finite timescale, we study domain walls moving at a constant velocity. We exploit an effective Lorentz invariance of the Hamiltonian to obtain an exact solution of the associated quasiparticle spectrum and wave functions for arbitrary velocities. Essential features of the solution have a natural interpretation in terms of the familiar relativistic effects of Lorentz contraction and time dilation. We find that the Majorana zero modes remain stable as long as the domain wall moves at subluminal velocities with respect to the effective speed of light of the system. However, the Majorana bound state dissolves into a continuous quasiparticle spectrum once the domain wall propagates at luminal or even superluminal velocities. This relativistic catastrophe implies that there is an upper limit for possible braiding frequencies even in a perfectly clean system with an arbitrarily large topological gap. We also exploit our exact solution to consider domain walls moving past static impurities present in the system.