A charge-driven feedback loop in the resonance fluorescence of a single quantum dot

TL;DR

This paper demonstrates a charge-driven feedback loop in a quantum dot system that stabilizes emission frequency and reduces spectral diffusion, enhancing photon coherence for quantum information applications.

Contribution

It introduces a fast, charge-based feedback mechanism that induces hysteresis and bistability, improving emission stability beyond previous nuclear spin feedback methods.

Findings

Feedback loop causes hysteresis and bistability in resonance fluorescence

Charge fluctuations span over 30 GHz, affecting emission stability

Potential to stabilize emission within milliseconds

Abstract

Semiconductor quantum dots can emit antibunched, single photons on demand with narrow linewidths. However, the observed linewidths are broader than lifetime measurements predict, due to spin and charge noise in the environment. This noise randomly shifts the transition energy and destroys coherence and indistinguishability of the emitted photons. Fortunately, the fluctuations can be reduced by a stabilization using a suitable feedback loop. In this work we demonstrate a fast feedback loop that manifests itself in a strong hysteresis and bistability of the exciton resonance fluorescence signal. Field ionization of photogenerated quantum dot excitons leads to the formation of a charged interface layer that drags the emission line along over a frequency range of more than 30 GHz. This internal charge-driven feedback loop could be used to reduce the spectral diffusion and stabilize the emission frequency within milliseconds, presently only limited by the sample structure, but already faster than nuclear spin feedback.