Credit: Tobias Heindel
The schematic illustrates the microlens device to measure dark excitons in a quantum dot. The left diagram depicts the spin-blockaded biexciton state that relaxes into a dark exciton and produces a photon; solid circles are electrons while empty ones are holes. The dark exciton then undergoes precession. To read the dark exciton, an extra charge carrier is introduced -- in this case, a spin-down electron.