Fig. 1
From: Quantum dot single-photon sources with ultra-low multi-photon probability

Two-photon excitation scheme. a Gate voltage dependent photoluminescence. b Schematic illustration of resonant excitation of a 2LS and two-photon excitation of 2X. Solid arrows represent laser drive, while dotted arrows represent spontaneous emission. c Example spectrum for two-photon excitation of 2X at 912.34 nm. d Rabi oscillations between \(\left| 0 \right\rangle\) and \(\left| {2X} \right\rangle\), measured from 2X luminescence