Chocolate Chips & Relaxed Quantum Dots ft. Armando Rastelli

In this episode

• What epitaxial quantum dots are, explained with a chocolate chip in a five-kilometre muffin, and how they differ from the colloidal dots in TV screens
• Why these dots matter for secure communication, and how rings around the source steer single photons in one direction
• How Armando went from taking gadgets apart as a child and detecting cosmic particles under a mountain to a professorship at Johannes Kepler University Linz
• The project he is proudest of: quantum dots grown without strain, first seen at 6am after a night in the lab and now taking over the field 20 years later
• How he once peeled graphene off graphite with sticky tape, and threw it away
• Quantum Science Austria, QuanTour’s travelling light source, and his one wish: less bureaucracy in science

Key Takeaways

• Professor at Johannes Kepler University Linz making epitaxial quantum dots (~50 nm wide, ~7 nm tall), ‘chocolate chips in a 5-km muffin’, for optoelectronic and quantum-light applications.
• Colloidal quantum dots (spherical, 2023 Nobel) go into bright TV screens; epitaxial dots are better for lasers and single/entangled-photon sources like the QuanTour source.
• The QuanTour ‘bullseye’ cavity is a specialised high-efficiency lens with a back mirror that funnels ~90% of emitted single photons into a fibre.
• During his PhD he peeled graphite with Scotch tape to calibrate an STM and threw the flakes away, ‘I missed the Nobel Prize’.
• One wish: far less bureaucracy in grants and reporting. Co-leads QuanTour and the Quantum Science Austria (QuantA) fundamental-science cluster.

About the guest

Armando Rastelli is a Professor at the Institute of Semiconductor and Solid State Physics at Johannes Kepler University Linz in Austria, where his group works on semiconductor quantum dots.

Armando Rastelli curated the Real Scientists Nano Twitter account (@RealSci_Nano) from May 6 to May 10 2024. Read all of Armando’s tweets from that week.