Near transform-limited single photons from rapid-thermal annealed quantum dots

TL;DR

This study demonstrates that rapid thermal annealing can tune the emission wavelength of quantum dots without significantly degrading their single-photon emission quality, producing near transform-limited photons suitable for quantum communication.

Contribution

It shows that high-temperature RTA effectively tunes quantum dot emission while maintaining near transform-limited linewidths, a novel approach for quantum photonic device optimization.

Findings

Single-photon emission with near transform-limited linewidths

RTA induces controlled blueshift without degrading optical quality

Dephasing time T2 is only 1.5 times the Fourier limit T2=2T1

Abstract

Single-photon emitters are essential components for quantum communication systems, enabling applications such as secure quantum key distribution and the long-term vision of a quantum internet. Among various candidates, self-assembled InAs/GaAs quantum dots (QDs) remain highly promising due to their ability to emit coherent and indistinguishable photons, as well as their compatibility with photonic integration. In this work, we investigate the impact of post-growth rapid thermal annealing (RTA) on the quantum optical properties of single self-assembled QDs embedded in a p-i-n diode structure. The annealing process induces a controlled blueshift of the emission wavelength by promoting Ga in-diffusion and intermixing. Using resonance fluorescence measurements at cryogenic temperatures (4.2 K), we investigate the single-photon statistics, the emission linewidths, and coherence time $T_2$ of the emitted photons. Our results show that, despite the high annealing temperature of $760^\circ$C, the process does not degrade the optical quality of the quantum dots strongly. Instead, we observe single-photon emission with near transform-limited linewidths, where the dephasing time $T_2$ is only a factor 1.5 above the Fourier-limit $T_2=2T_1$. These findings demonstrate that rapid thermal annealing (RTA) serves as an effective tuning method that preserves the key single-photon emission properties and may help reduce undesirable effects such as non-radiative Auger recombination in quantum photonic applications.