Quantum optics using transition metal dichalcogenides

We have recently started a new activity on quantum optics with 2D van der Waals materials.

Van der Waals materials are a family of layered materials with a large variety of physical properties. Using mechanical exfoliation they can be thinned down to the monolayer level and stacked on top of each other to form heterostructures with designed properties. We use monolayer transition metal dichalcogenides (TMDs), a semiconductor material with a direct band gap. Incident photons can promote electrons from the filled valence band to the conduction band. The electron forms a bound state with the positively charged hole that is left behind in the valence band called excitons. In TMDs, excitons have a particularly large binding energy due to the two-dimensional nature. Additionally, the excitons in TMDs couple to light much stronger than in other materials which makes them perfect for quantum optics experiments.

We explore and utilize the quantum nature of excitons. Therefore, we work with samples cooled down to cryogenic temperatures (4 Kelvin). In the context of our project within the ML4Q, we aim for heterostructures that allow for control and spatial confinement of excitons and coupling to a tunable fiber cavity with a small mode volume. In this way, the so-called strong coupling regime can be reached where the excitons hybridize with the cavity photons and form a new particle, the polariton. Scaling up such a system to many emitters offers possibilities to study new aspects of quantum computation and photonic interfacing with many-body quantum states.