Quantum Optics and Sensing using Nanophotonics and Solid-State Quantum Emitters

Our group focuses on efficient light-matter interfaces in the fields of solid-state quantum optics and sensing. Quantum emitters are not only key for applications such as sensing but play an essential part in new developments in quantum technology. Photons on the other hand have proven excellent carriers of information. They can be manipulated to high precision, are well shielded from decoherence by the environment and can be guided for long distances with low loss using optical fibers. With the aim to realise small and scalable systems that can be used as constituents in photonic quantum networks or as precise sensors, solid state quantum emitters have moved into focus. They are able to provide similar level structures compared to isolated atoms but can be more easily manipulated and integrated in different kinds of photonic networks or nanostructures. The guided modes of nanophotonic waveguides exhibit a pronounced evanescent field that allows for sensitive detection of even individual molecules or atoms in their surrounding. These waveguides can also be combined with microcavities to further enhance the light-matter interaction and make strong coupling between a light field and a single quantum emitter possible. We have shown the coherent interaction of single molecules in nanocrystals with the guided light field of an optical nanofiber. The subwavelengh diameter waist of these waveguides was achieved by tapering a commercial optical fiber using a heat and pull process.

We are now working towards an efficient light-matter interface using nanophotonic waveguides on chips and solid-state quantum emitters such as molecules in solids or colour centers in hexagonal Boron Nitride within the framework of the FETOpen project ErBeStA. As many solid-state quantum emitters require cryogenic temperatures to freeze out the phonons of the host system and avoid dephasing and inelastic scattering, most experiments so far have been conducted below 4 K. We were recently able to demonstrate that an alignment-free microcavity based on fiber Bragg gratings and an optical nanofiber can be used at cryogenic temperatures and may provide a promising platform for a strong light-matter interface. In addition we are also planning to move the field of solid-state quantum optics to room temperature.

Quantum emitters in hBN are a promising system to achieve this goal and we are currently working on a new experiment that was recently funded by an ESQ Discovery Grant.

We are very happy that our work on 2D materials has attracted more funding. Our new project PhoQus2D is funded by the FFG and will be conducted in collaboration with the group of Nanomaterials Synthesis and Integration of the TU Wien. We are always looking for motivated students or PostDocs to join us in our efforts to further advance solid-state quantum optics and apply quantum technology and nanophotonics for sensing applications.