Strain-mediated coupling in a quantum dot-mechanical oscillator hybrid system

TL;DR

This paper reports the experimental realization of a hybrid quantum system where a quantum dot embedded in a nanowire is coupled to mechanical vibrations via strain, achieving ultra-strong exciton-phonon coupling.

Contribution

The study demonstrates a monolithic solid-state hybrid system with strain-mediated coupling reaching the ultra-strong regime, advancing quantum nanomechanics and quantum information applications.

Findings

Achieved nearly ultra-strong exciton-phonon coupling with $g_0/2 ext{ extpi}$ close to mechanical frequency.

Demonstrated large light extraction efficiency and strong strain-mediated interaction.

Observed discrete mechanical resonances influencing quantum dot transition energies.

Abstract

Recent progress in nanotechnology has allowed to fabricate new hybrid systems where a single two-level system is coupled to a mechanical nanoresonator. In such systems the quantum nature of a macroscopic degree of freedom can be revealed and manipulated. This opens up appealing perspectives for quantum information technologies, and for the exploration of quantum-classical boundary. Here we present the experimental realization of a monolithic solid-state hybrid system governed by material strain: a quantum dot is embedded within a nanowire featuring discrete mechanical resonances corresponding to flexural vibration modes. Mechanical vibrations result in a time-varying strain field that modulates the quantum dot transition energy. This approach simultaneously offers a large light extraction efficiency and a large exciton-phonon coupling strength $g_0$. By means of optical and mechanical spectroscopy, we find that $g_0/2\pi$ is nearly as large as the mechanical frequency, a criterion which defines the ultra-strong coupling regime.