# Efficient Pulse-Excitation Techniques for Single Photon Sources from Quantum Dots in Cavities

## TL;DR

This paper models and compares three pulse-excitation methods for quantum dot single photon sources, demonstrating high efficiency and indistinguishability, with off-resonant schemes offering robustness and simplified analysis.

## Contribution

It introduces rigorous master equation models for pulse-excited quantum dot photon sources, analyzing their efficiency, purity, and indistinguishability, and provides a semi-analytical approach for off-resonant excitation.

## Key findings

- Near-unity indistinguishability with over 90% efficiency achieved.
- Off-resonant schemes do not require polarization filtering.
- Off-resonant methods are robust and less sensitive to pulse duration.

## Abstract

We present rigorous and intuitive master equation models to study on-demand single photon sources from pulse-excited quantum dots coupled to cavities. We consider three methods of source excitation: resonant pi-pulse, off-resonant phonon-assisted inversion, and two-photon excitation of a biexciton-exciton cascade, and investigate the effect of the pulse excitation process on the quantum indistinguishability, efficiency, and purity of emitted photons. By explicitly modelling the time-dependent pulsed excitation process in a manner which captures non-Markovian effects associated with coupling to photon and phonon reservoirs, we find that photons of near-unity indistinguishability can be emitted with over 90% efficiency for all these schemes, with the off-resonant schemes not necessarily requiring polarization filtering due to the frequency separation of the excitation pulse, and allowing for very high single photon purities. Furthermore, the off-resonant methods are shown to be robust over certain parameter regimes, with less stringent requirements on the excitation pulse duration in particular. We also derive a semi-analytical simplification of our master equation for the off-resonant drive, which gives insight into the important role that exciton-phonon decoupling for a strong drive plays in the off-resonant phonon-assisted inversion process