Quantum dot single photon sources with ultra-low multi-photon probability

TL;DR

This paper demonstrates that two-photon excitation of quantum dots significantly reduces multi-photon errors in single-photon sources, advancing quantum communication technologies.

Contribution

The study introduces a novel two-photon excitation scheme for quantum dots that suppresses re-excitation, improving single-photon purity over traditional resonant excitation methods.

Findings

Quadratic pulse-length dependence of multi-photon error rate

Order-of-magnitude reduction in multi-photon errors for short pulses

Development of a new theoretical framework for few-photon sources

Abstract

High-quality sources of single photons are of paramount importance for quantum communication, sensing and metrology. To these ends, resonantly excited two-level systems based on self-assembled quantum dots have recently generated widespread interest. Nevertheless, we have recently shown that for resonantly excited two-level systems, emission of a photon during the presence of the excitation laser pulse and subsequent re-excitation results in a degradation of the obtainable single-photon purity. Here, we demonstrate that generating single photons from self-assembled quantum dots with a scheme based on two-photon excitation of the biexciton strongly suppresses the re-excitation. Specifically, the pulse-length dependence of the multi-photon error rate reveals a quadratic dependence in contrast to the linear dependence of resonantly excited two-level systems, improving the obtainable multi-photon error rate by several orders of magnitude for short pulses. We support our experiments with a new theoretical framework and simulation methodology to understand few-photon sources.