Spin qubits in graphene quantum dots

TL;DR

This paper proposes a method to form and couple spin qubits in graphene quantum dots, overcoming valley degeneracy issues and enabling long-distance interactions due to graphene's unique spectrum.

Contribution

It introduces a way to lift valley degeneracy in graphene quantum dots using semiconducting armchair boundaries and demonstrates long-distance qubit coupling capabilities.

Findings

Bound states with specific energies and wave functions identified

Spin qubits can be coupled via Heisenberg exchange

Long-distance qubit coupling possible in graphene

Abstract

We propose how to form spin qubits in graphene. A crucial requirement to achieve this goal is to find quantum dot states where the usual valley degeneracy in bulk graphene is lifted. We show that this problem can be avoided in quantum dots based on ribbons of graphene with semiconducting armchair boundaries. For such a setup, we find the energies and the exact wave functions of bound states, which are required for localized qubits. Additionally, we show that spin qubits in graphene can not only be coupled between nearest neighbor quantum dots via Heisenberg exchange interaction but also over long distances. This remarkable feature is a direct consequence of the quasi-relativistic spectrum of graphene.