Quantum technologies are primed to revolutionise the fields of communication, information processing, and simulation in the coming years. Similar to the contemporary technologies that underpin modern society, future quantum devices will likely build on a semiconductor heterostructure platform. However, conventional semiconductor heterostructures have fundamental limitations: they are based on combinations of epitaxially-grown and lattice-matched bulk materials, which constrains possible material combinations and prevents free engineering of the new quantum states required for future technologies. The emerging field of two-dimensional (2D) van der Waals (vdW) heterostructures offers an unprecedented opportunity to tackle these technological challenges. The remarkable flexibility in material combinations and tunability of their physical parameters positions them as a promising platform to realise novel quantum states with tailored properties.
The project Two-Dimensional Quantum Photonics (2DQP) aims to characterize, identify, engineer, and coherently manipulate localized quantum states in this platform. One spectacular example of a 2D quantum material is shown in the figure below. In this figure, two single sheets of atoms are stacked on top of each other but with a relative ‘twist’. The ‘twist’ creates a moire pattern, which is depicted in the ‘shadow’ beneath the two layers of atoms. This long-range periodic pattern fundamentally changes the electronic and optical properties of the new material. For instance, electrons can be trapped at specific sites in the pattern, and the distance between each site can be engineered by the choice of materials and twist angle. The distance between the electron traps determine how they can interact, and in certain conditions strong interactions emerge which fundamentally alters their behaviour – for instance the strong correlations can lead to magnetism or superconductivity. This opens unprecedented opportunities to engineer, probe, and exploit emergent quantum materials based on collective interactions. In the same quantum material, another opportunity arises: creating particles called excitons, which are an electron and a hole (an absence of an electron in the crystal) strongly coupled together, at the specific sites in the moire pattern. In this case, the exciton can ‘collapse’ to form a particle of light called a photon (the wavy line in the figure). As only one exciton can exist at a site at a time, this leads to an organized array of single photon sources. The properties of these photon sources are highly tunable, and may eventually be exploited as hardware for quantum communication technology or to investigate new types of collective interactions among the excitons based on topology that enable coherent transfer of quantum information on-chip.
