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

Abstract

Recent progress in nanotechnology has allowed the fabrication of new hybrid systems in which a single two-level system is coupled to a mechanical nanoresonator^{1,2,3,4,5,6,7,8,9}. In such systems the quantum nature of a macroscopic degree of freedom can be revealed and manipulated¹⁰. This opens up appealing perspectives for quantum information technologies¹¹, and for the exploration of the quantum–classical boundary. Here we present the experimental realization of a monolithic solid-state hybrid system governed by material strain¹²: a quantum dot is embedded within a nanowire that features 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^13,14 and a large exciton–phonon coupling strength g₀. By means of optical and mechanical spectroscopy, we find that g₀/2π is nearly as large as the mechanical frequency, a criterion that defines the ultrastrong coupling regime^{<a id="ref-link-abstract-15" title="Armour, A. D., Blencowe, M. P. & Schwab, K. C. Entanglement and decoherence of a micromechanical...}