Decoherence of Majorana qubits by noisy gates

TL;DR

This paper models the decoherence of Majorana-based topological qubits caused by thermal charge fluctuations on gates, highlighting the impact of thermal but not quantum fluctuations, and offers design guidelines to mitigate decoherence.

Contribution

It introduces a realistic model for Majorana qubit decoherence due to thermal charge noise and provides practical criteria for optimizing gate design to minimize decoherence effects.

Findings

Quantum fluctuations do not cause decoherence.

Thermal fluctuations lead to decay of Majorana qubits.

Guidelines for gate design to reduce thermal decoherence.

Abstract

We propose and study a realistic model for the decoherence of topological qubits, based on Majorana fermions in one-dimensional topological superconductors. The source of decoherence is the fluctuating charge on a capacitively coupled gate, modeled by non-interacting electrons. In this context, we clarify the role of quantum fluctuations and thermal fluctuations and find that quantum fluctuations do not lead to decoherence, while thermal fluctuations do. We explicitly calculate decay times due to thermal noise and give conditions for the gap size in the topological superconductor and the gate temperature. Based on this result, we provide simple rules for gate geometries and materials optimized for reducing the negative effect of thermal charge fluctuations on the gate.