European quantum scientists flip excitons like light switches

Researchers from the University of Innsbruck, in collaboration with universities in Dortmund, Bayreuth, and Linz, have developed a novel technique to control dark excitons in semiconductor quantum dots using chirped laser pulses and magnetic fields. Excitons are quasiparticles formed when an electron is excited to a higher energy state, leaving behind a positively charged hole; the electron and hole pair orbit each other due to Coulomb attraction. Excitons are categorized as bright or dark based on their interaction with light: bright excitons can absorb or emit photons, while dark excitons, likely due to differing spin configurations, do not interact optically and thus have longer lifetimes, making them promising for energy storage and quantum information applications. The team demonstrated the ability to switch bright excitons into dark excitons and vice versa, effectively using dark excitons as a quantum memory by storing quantum states in a non-radiative form and reactivating them later with laser pulses. This controlled manipulation opens new avenues