Electric-field-induced coherent coupling of the exciton states in a single quantum dot

TL;DR

This paper demonstrates a method to control and observe coherent coupling between exciton states in a single quantum dot using an electric field, enabling entangled photon pair generation.

Contribution

It introduces a technique to electrically tune the energy splitting of exciton states, revealing their coherent coupling and enabling quantum control in a single quantum dot.

Findings

Electric field controls exciton energy splitting.

Observation of eigenstate rotation at minimal splitting.

Generation of entangled photon pairs.

Abstract

The signature of coherent coupling between two quantum states is an anticrossing in their energies as one is swept through the other. In single semiconductor quantum dots containing an electron-hole pair the eigenstates form a two-level system that can be used to demonstrate quantum effects in the solid state, but in all previous work these states were independent. Here we describe a technique to control the energetic splitting of these states using a vertical electric field, facilitating the observation of coherent coupling between them. Near the minimum splitting the eigenstates rotate in the plane of the sample, being orientated at 45{\deg} when the splitting is smallest. Using this system we show direct control over the exciton states in one quantum dot, leading to the generation of entangled photon pairs.