Controlling coherence between waveguide-coupled quantum dots

TL;DR

This paper introduces a waveguide with a split-diode structure enabling independent electrical tuning of multiple quantum dot emitters, facilitating the study of collective emission phenomena like superradiance.

Contribution

The novel waveguide design allows independent control of quantum dot transition energies and systematic exploration of superradiant to independent emission transition.

Findings

Observation of anti-dips in photon coincidences indicating collective emission.

Detection of lifetime drops around zero detuning showing superradiant behavior.

Identification of detuning regions with both superradiant enhancement and persistent correlations.

Abstract

We present a novel waveguide design that incorporates a split-diode structure, allowing independent electrical control of transition energies of multiple emitters over a wide range with minimal loss in waveguide coupling efficiency. We use this design to systematically map out the transition from superradiant to independent emission from two quantum dots. We perform both lifetime as well as Hanbury Brown-Twiss measurements on the device, observing anti-dips in the photon coincidences indicating collective emission while at the same time observing a drop in lifetime around zero detuning, indicating superradiant behaviour. Performing both measurement types allows us to investigate detuning regions which show both superradiant rate enhancement and inter-emitter coherence, as well as regions in which correlations persist in the absence of rate enhancement.