Nano Lett. 14, 456–463 (2014)

Hanbury-Brown and Twiss (HBT) interferometry is a fundamental measurement technique for investigating the quantum coherence of light sources. David Rivas and co-workers from Spain and Italy have now demonstrated a switchable two-colour excitation method based on HBT interferometry for evaluating the exciton and noncorrelated electron–hole dynamics associated with single-photon emission from InAs quantum dots. A single quantum dot is optically excited by light from an 830 nm laser alone, by light from a 790 nm laser alone and by light from both lasers; these three excitation schemes respectively generate neutral excitons, negative trions, and both neutral excitons and negative trions. The simultaneous emission of both excitons and trions results in two-colour emission. To prevent emission from multi-exciton states, the pumping powers of the 830 nm and 790 nm lasers were selected to be 76 nW and 20 μW, respectively. The researchers propose that the simultaneous detection of two-colour, single-photon emission from InAs quantum dots could be used to design a NAND logic gate function.