# Phonon Decoherence of Quantum Dots in Photonic Structures: Broadening of the Zero-Phonon Line and the Role of Dimensionality

## TL;DR

This paper presents a microscopic theory of phonon-induced decoherence in quantum dots within various photonic structures, revealing how dimensionality influences coherence and photon indistinguishability, with implications for quantum photonics.

## Contribution

The study introduces a general microscopic model linking phonon decoherence to structure dimensionality, highlighting the temperature-dependent dephasing behaviors in 0D, 1D, 2D, and 3D systems.

## Key findings

- Bulk dephasing rate scales as T^{11}, effectively freezing phonons below 4 K.
- 1D and 2D structures exhibit linear temperature scaling of dephasing.
- Photon indistinguishability is significantly affected even at sub-Kelvin temperatures.

## Abstract

We develop a general microscopic theory describing the phonon decoherence of quantum dots and indistinguishability of the emitted photons in photonic structures. The coherence is found to depend fundamentally on the dimensionality of the structure resulting in vastly different performance for quantum dots embedded in a nano-cavity (0D), waveguide (1D), slab (2D), or bulk medium (3D). In bulk, we find a striking temperature dependence of the dephasing rate scaling as $T^{11}$ implying that phonons are effectively 'frozen out' for $T \lesssim 4 \mathrm{K}$. The phonon density of states is strongly modified in 1D and 2D structures leading to a linear temperature scaling for the dephasing strength. The resulting impact on the photon indistinguishability can be important even at sub-Kelvin temperatures. Our findings provide a comprehensive understanding of the fundamental limits to photon indistinguishability in photonic structures.