The Origin of Antibunching in Resonance Fluorescence

TL;DR

This paper investigates whether subnatural linewidth photons from resonantly excited quantum dots can exhibit antibunching, concluding that such simultaneous features are not achievable with simple resonant excitation due to interference effects.

Contribution

The study provides experimental evidence that antibunching and subnatural linewidth cannot coexist in simple resonant excitation, aligning with recent theoretical models.

Findings

Antibunching disappears when filtering at the homogeneous linewidth.

Single-photon character confirmed via antibunching measurements.

Subnatural linewidth confirmed through high-resolution spectroscopy.

Abstract

Epitaxial quantum dots have emerged as one of the best single-photon sources, not only for applications in photonic quantum technologies but also for testing fundamental properties of quantum optics. One intriguing observation in this area is the scattering of photons with subnatural linewidth from a two-level system under resonant continuous wave excitation. In particular, an open question is whether these subnatural linewidth photons exhibit simultaneously antibunching as an evidence of single-photon emission. Here, we demonstrate that this simultaneous observation of subnatural linewidth and antibunching is not possible with simple resonant excitation. First, we independently confirm single-photon character and subnatural linewidth by demonstrating antibunching in a Hanbury Brown and Twiss type setup and using high-resolution spectroscopy, respectively. However, when filtering the coherently scattered photons with filter bandwidths on the order of the homogeneous linewidth of the excited state of the two-level system, the antibunching dip vanishes in the correlation measurement. Our experimental work is consistent with recent theoretical findings, that explain antibunching from photon-interferences between the coherent scattering and a weak incoherent signal in a skewed squeezed state.