# Enhancement of Femtosecond Photon Echo Signals From an Inhomogeneously Broadened InAs Quantum Dot Ensemble Using Chirped Pulses

## TL;DR

Researchers used chirped pulses to enhance photon echo signals in InAs quantum dots, enabling better optical quantum memory.

## Contribution

The study introduces chirped rephasing pulses for coherent control in THz-broadened quantum dot ensembles.

## Key findings

- Chirped pulses enable uniform population inversion and broadband rephasing in InAs quantum dots.
- A 3.2-fold enhancement of the photon-echo signal was experimentally observed.
- Numerical simulations validated the effectiveness of adiabatic rapid passage in this system.

## Abstract

Photon echo (PE) techniques offer a promising approach to optical quantum memory, yet their implementation in conventional platforms, such as rare‐earth‐ion‐doped crystals, is hindered by limited bandwidths. Semiconductor quantum dot (QD) ensembles, featuring THz‐scale inhomogeneous broadening and sub‐picosecond dynamics, provide an attractive alternative for ultrafast applications. However, achieving coherent control across such broad spectral ranges remains challenging due to detuning and spatial field inhomogeneities, which reduce PE efficiency. In this work, we demonstrate that chirped rephasing pulses satisfying adiabatic conditions enable robust adiabatic rapid passage (ARP) across an inhomogeneously broadened InAs QD ensemble. This approach achieves uniform population inversion and broadband rephasing, overcoming the limitations of transform‐limited excitation. Experimentally, we observe a 3.2‐fold enhancement of the PE signal in dense, self‐assembled InAs QDs operating at telecom wavelengths. Numerical simulations based on a two‐level model reproduce the experimentally observed ARP‐induced enhancement, validating the underlying physical mechanism. These results establish ARP as an effective and scalable method for coherent control in THz‐broadened QD ensembles, opening a pathway toward ultrafast and broadband optical quantum memory and communication in the telecom band.

Chirped rephasing pulses satisfying adiabatic conditions enable robust adiabatic rapid passage across a THz‐broadened InAs quantum dot ensemble. This approach provides uniform population inversion and broadband rephasing, overcoming the limitations of transform‐limited excitation. Experimentally, a 3.2‐fold enhancement of the photon‐echo signal is observed, demonstrating a scalable route toward ultrafast and broadband optical quantum memory.