Controlling coherence between waveguide-coupled quantum dots

We present a waveguide design incorporating 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 through control of the emitter detuning. We perform both lifetime and Hanbury Brown-Twiss measurements on the device, observing antidips in the photon coincidences—indicating collective emission, while at the same time observing a drop in lifetime around zero detuning—indicating superradiant behavior. Performing both measurements allows us to investigate detuning regions, which show both superradiant rate enhancement and interemitter coherence, as well as regions in which correlations persist in the absence of rate enhancement.