Towards Photon-Number-Encoded High-dimensional Entanglement from a Sequentially Excited Quantum Three-Level System

TL;DR

This paper demonstrates the experimental generation of photon-number-encoded high-dimensional entanglement using a sequential excitation of a semiconductor quantum dot's three-level system, advancing quantum communication capabilities.

Contribution

It reports the first experimental realization of photon-number-encoded entanglement from a three-level quantum system, extending previous two-level system methods.

Findings

Generated entangled states exhibit time and energy entanglement.

Energy- and time-resolved correlation experiments confirm entanglement.

Theoretical modeling supports the experimental observations.

Abstract

The sequential resonant excitation of a 2-level quantum system results in the emission of a state of light showing time-entanglement encoded in the photon-number-basis - notions that can be extended to 3-level quantum systems as discussed in a recent proposal. Here, we report the experimental implementation of a sequential two-photon resonant excitation process of a solid-state 3-level system, constituted by the biexciton-, exciton-, and ground-state of a semiconductor quantum dot. The resulting light state exhibits entanglement in time and energy, encoded in the photon-number basis, which could be used in quantum information applications, e.g., dense information encoding or quantum communication protocols. Performing energy- and time-resolved correlation experiments in combination with extensive theoretical modelling, we are able to partially retrieve the entanglement structure of the generated state.