Single nano-scale emitters in semiconductors

Ambitious EU-funded researchers set out to explore quantum interactions within the scope of the project 'Demonstration of superradiance in a semiconductor nanostructure' (SUPERRAD). Despite obstacles related to high equipment costs and unavailability of high-purity samples, by completion the team had achieved world-class results.

The scope of the project turned toward coherent non-linear spectroscopy, significantly advancing the current state of the art and delivering groundbreaking outcomes regarding individual emitters in solids.

Scientists developed a novel spectroscopic technique using short optical pulses from three beams. The pulses resonantly drive a non-linear response in single excitons (a dipole moment created by an electron–hole pair) in strongly confined quantum dots. The setup performs much better than the previous generation, until recently available in only one lab in the world.

With it, the team carried out seminal experiments on single excitons using four-wave mixing and six-wave mixing protocols exploiting the interaction of four or six coherent optical fields. Researchers were able to dramatically enhance the retrieval efficiency of coherent responses of single quantum dots in semiconductors. Quantum information processing relies on coherent and reversible mapping between light and matter, so this is of great significance.

Numerous publications in prestigious peer-reviewed journals, including Nature Materials, Nature Communications and Nature Photonics, have highlighted the work. The technique opens the door to exploration of numerous materials and behaviours, including the spatial propagation of coherence, and has established the project head as a leader in the field.