Rapid Optical Spin Initialization of a Quantum Dot in the Voigt Geometry Coupled to a Two-Dimensional Semiconductor

Dionisis Stefanatos,Emmanuel Paspalakis,Nikos Iliopoulos,Vasilios Karanikolas

doi:10.3390/app10031001

Abstract

We study the interaction of a quantum dot in the Voigt configuration with a laser pulse and particularly analyze the potential for rapid spin initialization by putting the quantum dot near a molybdenum disulfide (MoS 2 ) monolayer. The MoS 2 monolayer influences the spontaneous decay rates of the quantum dot, leading to anisotropically enhanced decay rates, for the quantum dot’s electric dipole moments parallel and perpendicular to the layer. By solving the relevant density matrix equations, we find that high spin initialization fidelity is obtained at short times. The fidelity is significantly higher than when the quantum dot is in free-space vacuum. We examine two different cases of the interaction of the quantum dot with the applied optical field. First, we use a continuous wave laser field and determine for various quantum dot—MoS 2 layer distances the field strength that leads to acceptable fidelity levels. The effect of the quality of the MoS 2 material on the fidelity of spin initialization is also examined. We also study the interaction of the quantum dot with a laser pulse and apply numerical optimal control to obtain the time-dependent field strength, which leads to maximum final fidelity for short time intervals. The latter approach gives beneficial results in comparison to the continuous wave field excitation.

Highlights

Quantum dots (QDs), known as “artificial atoms”, are primary candidates for quantum information technologies [1]
We study the interaction of the QD with a laser pulse and apply numerical optimal control, using a state-of-the-art optimal control solver, to obtain the time-dependent field strength, which leads to maximum final fidelity for short time intervals
We continued our studies in accelerating spin initialization for a QD in the Voigt configuration using nearby two-dimensional materials [22] by studying the problem of a QD near a

Summary

Introduction

Quantum dots (QDs), known as “artificial atoms”, are primary candidates for quantum information technologies [1]. The key to their proposal is to create an anisotropic Purcell-enhanced decay rate from the trion state to the target electron spin state by coupling the QD with a photonic structure. Our group proposed the coupling of a QD in the Voigt geometry with a graphene monolayer, the basic two-dimensional material, for obtaining high fidelity electron spin initialization in short time intervals [22]. The spontaneous decay rates for a quantum emitter near a MoS2 layer can be anisotropic for electric dipole moments parallel or perpendicular to the monolayer [28], which makes the MoS2 layer a potential candidate for accelerating the spin initialization process in a nearby QD in the Voigt geometry. The required anisotropically enhanced decay rates were obtained for a QD near a MoS2 monolayer

Rapid Spin Initialization with Optical Fields

Constant Control

Time-Dependent Control

Conclusions