arXiv subjects

A. Fenzl

Publications and source records attributed to A. Fenzl.

3 recordsLinked to original sources

arXiv2025

Chiral Quantum Optics with Scalable Quantum Dot Dimers

We present a scalable method for electrically tuning multiple spatially separated quantum dots embedded in photonic crystal waveguides. Ion implantation into the top p-doped layer of a p-i-n diode creates high-resistivity tracks, providing electrical isolation between adjacent regions. Unlike physical etching, this method preserves the guided-mode profile of the photonic crystal without introducing significant scattering, limiting refractive index perturbations to below 0.001 with 0.01% additional loss. In contrast, physical etching can reduce single-band transmission by more than 30% for an etch width of 100 nm. We demonstrate the applicability of our approach using quantum dots embedded in a glideplane photonic crystal waveguide, controlling the detuning between different spin-state combinations of two highly chiral quantum dots coupled to the same mode. Second-order photon correlation measurements provide a sensitive probe of the chirality-dependent photon statistics, which are in good agreement with a waveguide-QED master equation model. Our results mark an important step towards scalable, multi-emitter architectures for chiral quantum networks.

physics.optics↗

arXiv2024

Controlling coherence between waveguide-coupled quantum dots

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.

quant-ph↗

arXiv2024

Nonlinear Quantum Optics at a Topological Interface Enabled by Defect Engineering

The integration of topology into photonics has generated a new design framework for constructing robust and unidirectional waveguides, which are not feasible with traditional photonic devices. Here, we overcome current barriers to the successful integration of quantum emitters such as quantum dots (QDs) into valley-Hall (VH) topological waveguides, utilising photonic defects at the topological interface to stabilise the local charge environment and inverse design for efficient topological-conventional mode conversion. By incorporating QDs within defects of VH-photonic crystals, we demonstrate the first instances of single-photon resonant fluorescence and resonant transmission spectroscopy of a quantum emitter at a topological waveguide interface. Our results bring together topological photonics with optical nonlinear effects at the single-photon level, offering a new avenue to investigate the interaction between topology and quantum nonlinear systems.

physics.optics↗