# A solid state single photon source with Fourier Transform limited lines at room temperature

## TL;DR

This paper reports a breakthrough in solid state single photon sources by achieving Fourier Transform limited lines at room temperature using a color center in hexagonal boron nitride, advancing quantum photonics.

## Contribution

The study demonstrates FT limited lines from a 2D material at room temperature, revealing decoupling from phonons due to low dimensionality, and proposes methods to mitigate spectral diffusion.

## Key findings

- FT limited lines observed from 3K to 300K
- Decoupling from phonons attributed to low dimensionality
- Spectral diffusion identified and mitigated through dynamic tuning

## Abstract

Solid state single photon sources with Fourier Transform (FT) limited lines are among the most crucial constituents of photonic quantum technologies and have been accordingly the focus of intensive research over the last several decades. However, so far, solid state systems have only exhibited FT limited lines at cryogenic temperatures due to strong interactions with the thermal bath of lattice phonons. In this work, we report a solid state source that exhibits FT limited lines measured in photo luminescence excitation (sub 100 MHz linewidths) from 3K-300K. The studied source is a color center in the two-dimensional hexagonal boron nitride and we propose that the center's decoupling from phonons is a fundamental consequence of material's low dimensionality. While the center's luminescence lines exhibit spectral diffusion, we identify the likely source of the dffusion and propose to mitigate it via dynamic spectral tuning. The discovery of FT-limited lines at room temperature, which once the spectral diffusion is controlled, will also yield FT-limited emission. Our work motivates a significant advance towards room temperature photonic quantum technologies and a new research direction in the remarkable fundamental properties of two-dimensional materials.