# Resolving the temporal evolution of line broadening in quantum emitters

## TL;DR

This paper uses photon correlation Fourier spectroscopy to study how environmental factors cause line broadening in quantum emitters over time, revealing differences between exciton and biexciton emissions and assessing the impact of white light irradiation.

## Contribution

It introduces the application of PCFS to analyze the temporal evolution of line broadening in quantum dots with high spectral and temporal resolution, outperforming traditional methods.

## Key findings

- Distinct temporal evolution of line broadening for exciton and biexciton lines.
- White light irradiation reduces blinking but increases charge noise.
- PCFS provides high-resolution, robust measurements suitable for quantum communication applications.

## Abstract

Light emission from solid-state quantum emitters is inherently prone to environmental decoherence, which results in an inhomogeneous line broadening and in the deterioration of photon indistinguishability. Here we employ photon correlation Fourier spectroscopy (PCFS) to study the temporal evolution of such a broadening for the biexciton and exciton emission in resonantly driven GaAs quantum dots. Differently from previous experiments, the time scales we probe range from a few nanoseconds to milliseconds and, simultaneously, the spectral resolution we achieve can be as small as 2 $\mu$eV. We find pronounced differences in the temporal evolution of the two lines, which we attribute to differences in their homogeneous linewidth and sensitivity to charge noise. We then analyze the effect of irradiation with additional white light, which reduces blinking at the cost of enhanced charge noise. Due to its robustness against experimental imperfections and its high temporal resolution and bandwidth, PCFS outperforms established spectroscopy techniques, such as Michelson interferometry. We discuss its practical implementation, its limitations, and the possibility to use it to estimate the indistinguishability of consecutively emitted single photons for applications in quantum communication and photonic-based quantum information processing.